UV curable elastomer composition

ABSTRACT

Ethylene copolymer elastomer compositions, acrylate rubber compositions, nitrile rubber compositions, fluoroelastomer compositions, and chlorinated olefin elastomer compositions are provided which are curable by exposure to UV radiation. The compositions are particularly suited for production of elastomeric seals using hot melt equipment and a gasketing in place technique.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of application Ser. No. 09/842,430 filed Apr. 26,2001 now U.S. Pat. No. 6,506,460 which is a division of application Ser.No. 09/353,982, filed Jul. 15, 1999, now U.S. Pat. No. 6,346,300 issuedFeb. 12, 2002, which is a continuation-in-part of application Ser. No.09/234,014, filed Jan. 19, 1999, now abandoned, which claims the benefitof U.S. Provisional Application No. 60/072,109 filed Jan. 21, 1998.

FIELD OF THE INVENTION

This invention relates to elastomeric compositions that are curable byexposure to ultraviolet (UV) radiation. In addition, this inventionrelates to a process for curing elastomeric seals rapidly, wherein theseals are formed by applying an uncured polymer composition directlyonto a sealing element or a surface to be sealed. This invention furtherrelates to cured articles produced by the process of the invention.

BACKGROUND OF THE INVENTION

Elastomeric compositions require a vulcanization, i.e. curing, step inorder to develop the crosslinked network structure which confers optimumrubbery properties to such compositions. Typically, the curing processesare based on compression molding or transfer molding techniques whereinan elastomer, fully compounded with curing agent and other additives, isintroduced into a mold that is then heated under pressure. The elevatedtemperatures used during the molding process cause chemical reaction ofthe elastomer and curative, thereby producing a crosslinked product.

The particular raw (i.e. uncured) elastomer used to manufacture asynthetic rubber article will be selected with reference to the specificend use application and environment under which the finished articlemust function. For example, one will select different elastomers fromamong ethylene alkyl acrylate copolymer rubbers, ethylene alpha-olefincopolymer elastomers, fluoroelastomers and chlorinated elastomersdepending upon whether the finished article will be exposed to oils,water, fuels, acids or bases. One will also consider the temperaturerange to which the article will be subjected and special requirementssuch as flame resistance. In addition, consideration will be given tothe cure characteristics of the polymer and the ease with whichdefect-free parts can be produced.

The majority of elastomeric seals manufactured on a commercial scale arecrosslinked at high temperature in molding processes. Generally,elastomeric seals and gaskets thus produced are manually fitted onto anarticle to be sealed. Alternatively, adhesives are sometimes utilized toattach the cured sealing member to an article. Such attachmenttechniques are not completely satisfactory in all cases. In particular,manual methods are time consuming and adhesives can affect the physicalproperties of the seal.

Elastomeric gaskets are often utilized as sealing members for groovedparts, such as rocker covers and air intake manifolds, that are used inautomobile engines. Such gaskets must be resistant to the effects ofheat and oil. Traditionally, cured, oil-resistant elastomercompositions, such as ethylene alkyl acrylate copolymer rubbers, havebeen manually introduced into the groove of a metal part. Manyautomotive components are now formed from high performance thermoplasticmaterials, rather than from metal. Manual fitting of elastomeric sealsonto these components is time-consuming, but curing the seal in place isimpractical because either the cure temperature or, in some cases, thepost cure temperature, is usually high enough to cause deformation ofthe thermoplastic. Yet, if the cure temperature is lowered, cure rate istoo slow to be practical. Oil or fuel resistant elastomeric compositionsthat could be readily applied to an article or groove in their uncuredstate and that are adapted to low temperature curing techniques wouldtherefore be especially useful in manufacture of thermoplastic articleshaving attached sealing members for automotive or industrial uses.

Low temperature curing processes that are initiated by high energyradiation, such as electron beam or γ-radiation, are known for use withalmost any elastomer, including ethylene acrylate copolymer elastomers.For example, electron beam crosslinking of wire and cable insulationcompositions, including elastomeric compositions, is disclosed in E.Brandt and A. Berejka, Electron Beam Crosslinking of Wire and CableInsulation, Rubber World, 49, November 1978. Eldred, in U.S. Pat. No.3,950,238, discloses the use of electron beam radiation to cureacrylonitrile butadiene polymers and Clarke, in U.S. Pat. No. 4,275,180,discloses the use of electron beam radiation cure of a blend of anethylene acrylate copolymer rubber and a thermoplastic polymer, e.g. forcable jacketing. Electron beam cures have the disadvantage of requiringquite complex and expensive equipment for generating high energyparticles. It would therefore be advantageous to have available a lowtemperature curing process that did not rely on the use of electron beamradiation. Low temperature UV cures of a variety of polymers, includingethylene acrylate polymers, are disclosed in U.S. Pat. No. 4,863,536.However, the disclosed process involves dissolution of the particularpolymer in an acrylate monomer and is not suitable for preparation ofgeneral rubber goods, such as gaskets and seals.

In addition to having available an effective low temperature cureprocess for ethylene acrylate copolymer elastomers, it would also beadvantageous to have available similar curing techniques for use withother elastomers as well. As is the case with ethylene acrylatecopolymers, typical curing processes for fluoroelastomers are based onhigh temperature compression molding or transfer molding techniques.Products made using such processes include seals, gaskets, tubing, andother general rubber goods. In addition, textile composites coated withfluoroelastomers are available commercially and are generally subjectedto a baking process during fabrication, for example as disclosed in U.S.Pat. No. 4,770,927 to Effenberger et al.

Low temperature radiation curing processes for fluoroelastomers areknown in the prior art. For example, a stain-resistant protectivefluoroelastomer coating composition for flooring that is curable usingUV radiation is disclosed in European Patent Application 570254. UV cureof epoxy-containing fluorinated copolymers is described in JapaneseKokai Patent Application 5-302058. In addition, UV or electron beamcures of certain fluoroelastomer compositions that are normally curedwith a polyol or polyamine crosslinking agent are disclosed in GermanPatent 19642029 and in Japanese Kokai Patent Application 61-031411.Blends of fluoroplastics and ethylene vinyl acetate copolymers orethylene acrylic acid ester copolymers that are cured with UV radiationare disclosed in Japanese Kokai Patent Application 5-078539.

These prior art compositions possess interesting properties, but they donot provide compositions that exhibit the tensile strength, modulus, andcompression set that is required in many commercial applications, forexample air intake manifold gaskets. There thus remains a need in theart for fluoroelastomer compositions that can be cured at lowtemperature by low energy radiation processes and that, when cured,exhibit excellent tensile strength, modulus, and compression set.

Similarly, chlorinated elastomers such as chlorinated polyethylene,chlorosulfonated polyethylene and epichlorohydrin rubber, aretraditionally crosslinked thermally by either ionic or free radical curesystems in compression molds. Extended high temperature exposure ofcurable compositions containing these polymers can be problematic due tothe tendency of these polymers to dehydrochlorinate. Because of the highcure temperatures required, these elastomers have little utility inapplications involving formation of elastomer/thermoplastic compositesthat are cured in place. Just as with ethylene alkyl acrylateelastomers, manufacture of chlorinated elastomer/thermoplastic compositearticles requires an elastomer that can be cured at a temperaturesufficiently low to preclude deformation of the thermoplastic. Lowtemperature UV cures of chlorinated polyolefin coating compositions areknown. U.S. Pat. No. 4,880,849 discloses a UV-curable chlorinatedpolyolefin coating having excellent adhesion to plastic substrates.Japanese Kokai Patent Application 63-267517 discloses UV cure ofchlorosulfonated polyethylene rubber and epichlorohydrin hose that isfirst passed through a UV irradiation apparatus and then vulcanized atelevated temperature for 30-60 minutes. However, chlorinated elastomercompositions that could be readily applied to a groove or an article intheir uncured state and that are adapted to low temperature curingtechniques are not known in the prior art.

There is thus a need for a method by which an elastomeric sealingcomposition may be applied to a substrate in an efficient, adhesive-freemanner and cured at low temperature to produce a cured seal that has anexcellent balance of tensile strength, modulus and compression set.

SUMMARY OF THE INVENTION

The present invention is directed to curable elastomeric compositionsthat are capable of being crosslinked at low temperatures. Inparticular, the present invention is directed to a thermally stable,curable elastomer composition comprising

a) 75 to 95 weight percent of an elastomer selected from the groupconsisting of

1) copolymers comprising ethylene and a comonomer selected from thegroup consisting of C₁-C₈ alkyl esters of acrylic acid, C₁-C₈ alkylesters of methacrylic acid, and vinyl esters of C₂-C₈ carboxylic acids;

2) alkyl acrylate polymers selected From the group consisting ofhomopolymers of C₁-C₁₀ alkyl acrylates and copolymers of C₁-C₁₀ alkylacrylates with up to 40 weight percent monovinyl monomers; and

3) diene copolymers selected from the group consisting of copolymers ofa diene and an unsaturated nitrile and hydrogenated copolymers of adiene and an unsaturated nitrile;

b) 2 to 24 weight percent of a multifunctional crosslinking agentselected from the group consisting of multifunctional acryliccrosslinking agents, multifunctional methacrylic crosslinking agents,multifunctional cyanurate crosslinking agents, and multifunctionalisocyanurate crosslinking agents; and

c) 0.2 to 5.0 weight percent of a UV initiator wherein the weightpercentages of each of components a), b), and c) are based on thecombined weight of components a), b), and c).

wherein the weight percentages of each of components a), b), and c) arebased on this combined weight of components a), b), and c).

The invention is further directed to a process for applying a seal to anarticle comprising the steps of

A) blending at a temperature of between 25° C. and 250° C.

1) 75 to 95 weight percent of an elastomer selected from the groupconsisting of

a) copolymers comprising ethylene and a comonomer selected from thegroup consisting of C₁-C₈ alkyl esters of acrylic acid, C₁-C₈ alkylesters of methacrylic acid, and vinyl esters of C₂-C₈ carboxylic acids;

b) alkyl acrylate polymers selected from the group consisting ofhomopolymers of C₁-C₁₀ alkyl acrylates and copolymers of C₁-C₁₀ alkylacrylates with up to 40 weight percent monovinyl monomers; and

c) diene copolymers selected from the group consisting of copolymers ofa diene and an unsaturated nitrile and hydrogenated copolymers of adiene and an unsaturated nitrile;

2) 2 to 24 weight percent of a multifunctional crosslinking agentselected from the group consisting of multifunctional acryliccrosslinking agents, multifunctional methacrylic crosslinking agents,multifunctional cyanurate crosslinking agents, and multifunctionalisocyanurate crosslinking agents; and

3) 0.2 to 5.0 weight percent of a UV initiator wherein the weightpercentages of each of components 1), 2), and 3) are based on thecombined weight of components 1), 2), and 3), to form a thermallystable, curable, extrudable mixture;

B) depositing said extrudable mixture on said article in the shape andthickness desired to form an uncured seal; and

C) irradiating said uncured seal with UV radiation for a time sufficientto cure said seal.

The present invention is also directed to curable fluoroelastomercompositions that are capable of being crosslinked at low temperatures.In particular, the present invention is directed to a thermally stable,curable elastomer composition comprising

A) 70 to 99 weight percent of a fluoroelastomer having at least one curesite selected from the group consisting of 1) copolymerized brominatedolefins, chlorinated olefins and iodinated olefins; 2) copolymerizedbrominated unsaturated ethers, chlorinated unsaturated ethers, andiodinated unsaturated ethers; 3) copolymerized non-conjugated dienes andtrienes and 4) iodine atoms, bromine atoms and mixtures thereof that arepresent at terminal positions of the fluoroelastomer chain;

B) 0.5 to 20 weight percent of a multifunctional crosslinking agentselected from the group consisting of multifunctional acryliccrosslinking agents, multifunctional methacrylic crosslinking agents,multifunctional cyanurate crosslinking agents, and multifunctionalisocyanurate crosslinking agents; and

C) 0.1 to 10 weight percent of a UV initiator wherein the weightpercentages of each of components A), B), and C) are based on thecombined weight of components A), B), and C).

The invention is further directed to a process for applying a seal to anarticle comprising the steps of

A) blending at a temperature of between 25° C. and 250° C.

1) 70 to 99 weight percent of a fluoroelastomer;

2) 0.5 to 20 weight percent of a multifunctional crosslinking agentselected from the group consisting of multifunctional acryliccrosslinking agents, multifunctional methacrylic crosslinking agents,multifunctional cyanurate crosslinking agents, and multifunctionalisocyanurate crosslinking agents; and

3) 0.1 to 10 weight percent of a UV initiator

 wherein the weight percentages of each of components 1), 2), and 3) arebased on the combined weight of components 1), 2), and 3), to form athermally stable, curable, extrudable mixture;

B) depositing said extrudable mixture on said article in the shape andthickness desired to form an uncured seal; and

C) irradiating said uncured seal with UV radiation for a time sufficientto cure said seal.

The present invention is also directed to curable chlorinated elastomercompositions that are capable of being crosslinked at low temperatures.In particular, the present invention is directed to a thermally stable,curable elastomer composition consisting essentially of

A) 80 to 97 weight percent of a chlorinated elastomer selected from thegroup consisting of chlorinated polyolefin elastomers andepichlorohydrin elastomers;

B) 2 to 19.5 weight percent of a multifunctional crosslinking agentselected from the group consisting of multifunctional acryliccrosslinking agents, multifunctional methacrylic crosslinking agents,multifunctional cyanurate crosslinking agents, and multifunctionalisocyanurate crosslinking agents; and

C) 0.2 to 5.0 weight percent of a UV initiator

wherein the weight percentages of each of components A), B), and C) arebased on the combined weight of components A), B), and C). In oneembodiment, the chlorinated olefin polymer is a chlorosulfonated olefinpolymer.

The invention is further directed to a process for applying a seal to anarticle comprising the steps of

A) blending at a temperature of between 25° C. and 250° C.

1) 80 to 97 weight percent of a chlorinated elastomer selected from thegroup consisting of chlorinated polyolefin elastomers andepichlorohydrin elastomers;

2) 2 to 19.5 weight percent of a multifunctional crosslinking agentselected from the group consisting of multifunctional acryliccrosslinking agents, multifunctional methacrylic crosslinking agents,multifunctional cyanurate crosslinking agents, and multifunctionalisocyanurate crosslinking agents; and

3) 0.2 to 5.0 weight percent of a UV initiator wherein the weightpercentages of each of components 1), 2), and 3) are based on thecombined weight of components 1), 2), and 3), to form a thermallystable, curable, extrudable mixture;

B) depositing said extrudable mixture on said article in the shape andthickness desired to form an uncured seal; and

C) irradiating said uncured seal with UV radiation for a time sufficientto cure said seal.

In addition, the present invention is directed to a process for applyinga seal to an article comprising the steps of

A) blending at a temperature of between 25° C. and 250° C.

1) 80-98 weight percent of an ethylene alpha-olefin copolymer comprisingethylene and a C₃-C₂₀ alpha-olefin;

2) 1-19.5 weight percent of a multifunctional crosslinking agentselected from the group consisting of multifunctional acryliccrosslinking agents and multifunctional methacrylic crosslinking agents;and

3) 0.2-5 weight percent of a UV initiator wherein the weight percentagesof each of components 1), 2), and 3) are based on the combined weight ofcomponents 1), 2), and 3), to form a thermally stable, curable,extrudable mixture;

B) depositing said extrudable mixture on said article in the shape andthickness desired to form an uncured seal; and

C) irradiating said uncured seal with UV radiation for a time sufficientto cure said seal.

The invention is also directed to cured articles produced by theseprocesses.

DETAILED DESCRIPTION OF THE INVENTION

The thermally stable, curable compositions of the present inventioncomprise an elastomer; a multifunctional crosslinking agent, generallyan acrylic or methacrylic crosslinking agent; and a UV initiator. Thesecurable compositions are utilized as starting materials in the processfor applying a seal to an article that is a further embodiment of theinvention. In preferred embodiments of the process of the invention, theelastomer, multifunctional crosslinking agent and UV initiator arepresent as three separate components. However, the UV initiator may bepresent as a chemically combined component with the elastomer. That is,the UV initiator may be chemically incorporated into the elastomericcomponent as a polymer-bound photoinitiator. Such polymer-boundphotoinitiators are disclosed, for example in U.S. Pat. No. 5,128,386wherein a photoinitiator is copolymerized with an acrylate copolymer.

The compositions are curable by the action of UV radiation. They arethermally stable at temperatures used to process uncured elastomerformulations, e.g. in mixing or extruding operations. Such temperaturesgenerally range from 25° C. to 250° C. By thermally stable is meant thatthe compositions do not spontaneously form a crosslinked network, i.e.they do not prematurely cure or scorch. That is, the viscosity of thecompositions remains constant, within ±50% of the initial value whenheated to the processing temperature, as indicated by lack of asubstantial increase in torque (i.e. an increase of less than 1 dNm)when subjected to the processing temperature for 30 minutes in a MovingDie Rheometer. The appropriate processing temperature will depend on thedecomposition temperature of the particular UV initiator andmultifunctional crosslinking agent that is employed. However, theprocessing temperature must be sufficiently high so that the curableelastomer composition flows to the degree required for the productionprocess. This temperature will generally be from 25° C. to 250° C.,preferably from 90° C. to 170° C. The compositions, when heated orsubjected to mechanical working, such as in a screw extruder, gear pump,or piston pump, are capable of viscoelastic flow and may be metered andformed into shaped articles, such as seals. These articles may then becured by exposure to UV radiation.

The elastomeric component of the thermally stable compositions of theinvention may be any of the members of the following classes of raw(i.e. uncured) elastomeric polymers: ethylene acrylate copolymerrubbers, ethylene methacrylate copolymer rubbers, acrylate rubbers,ethylene vinyl ester elastomers, elastomeric copolymers of a diene andan unsaturated nitrile (i.e., nitrile rubber and hydrogenated nitrile),fluoroelastomers having copolymerized units of iodinated, brominated, orchlorinated cure site monomers, fluoroelastomers having copolymerizedunits of non-conjugated dienes, fluoroelastomers having bromine oriodine atoms at terminal positions of the fluoroelastomer, chlorinatedolefin elastomers, chlorosulfonated olefin elastomers, andepichlorohydrin elastomers.

One class of ethylene copolymer rubbers useful in the composition andprocess of the invention is made up of two types of ethylene estercopolymers. The first type includes ethylene copolymers havingcopolymerized units of C₁-C₈ alkyl esters of acrylic acid or C₁-C₈ alkylesters of methacrylic acid. The second type includes ethylene copolymershaving copolymerized units of vinyl esters of C₂-C₈ carboxylic acids.Each of these types of copolymers includes dipolymers or higher ordercopolymers having copolymerized units of other comonomers.

When the copolymers are dipolymers, the ethylene content ranges fromabout 20-85 weight percent, preferably 30-65 weight percent.Representative examples of such compositions include copolymers ofethylene with, for example, methyl acrylate, ethyl acrylate, n-butylacrylate, isobutyl acrylate, 2-ethylhexyl acrylate, hexyl acrylate, andcopolymers of ethylene with, for example, vinyl acetate, vinylpropionate, and vinyl hexanoate. Copolymers of ethylene with, forexample, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate,2-ethylhexyl methacrylate, n-butyl methacrylate, or hexyl methacrylatemay also be employed, but ethylene acrylate copolymers and ethylenevinyl ester copolymers are preferred. Methyl acrylate, n-butyl acrylate,and vinyl acetate are among the most preferred comonomers. Thecopolymers generally have Mooney viscosities ranging from 1-60, ML 1+4(100° C.), preferably 1-20, ML 1+4 (100° C.). Blends of dipolymers mayalso be utilized.

Examples of higher order types of the foregoing elastomeric copolymersof ethylene which are suitable for use as the polymeric component of thecompositions of the present invention include copolymers of a) ethylene,b) alkyl acrylates, alkyl methacrylates, or vinyl esters of carboxylicacids, and c) unsaturated acids. Specific examples include terpolymershaving copolymerized units of a) ethylene, b) C₁-C₈ alkyl esters ofacrylic acid, C₁-C₈ alkyl esters of methacrylic acid, or vinyl esters ofC₂-C₈ carboxylic acids and c) carboxylic acids of 3-12 carbon atomsselected from the group consisting of alpha, beta-unsaturatedmonocarboxylic acids; alpha, beta-unsaturated dicarboxylic acids; andmonoesters of alpha, beta-unsaturated dicarboxylic acids. The ethylenecontent of the copolymers ranges from about 25-70 weight percent of thepolymer, preferably 35-65 weight percent, and the alpha,beta-unsaturated mono- or dicarboxylic acids or monoesters of alpha,beta-unsaturated acids are present in an amount sufficient to provide0.1-10 weight percent, preferably 0.5-5.0 weight percent, of carboxylicacid groups. Suitable alpha, beta-unsaturated mono- or dicarboxylicacids include monocarboxylic acids such as acrylic acid and methacrylicacid; dicarboxylic acids, such as maleic acid, fumaric acid, anditaconic acid; and monoesters of dicarboxylic acids such as ethylhydrogen maleate, ethyl hydrogen fumarate, and 2-ethylhexyl hydrogenmaleate. Acrylic acid, methacrylic acid, and ethyl hydrogen maleate arepreferred. The alkyl acrylate or the vinyl ester comonomers comprise25-70 weight percent of the polymer, preferably 30-65 weight percent.Alkyl acrylates suitable for use in the polymers include C₁-C₈ alkylesters of acrylic acid, for example, the methyl, ethyl, n-butyl,isobutyl, hexyl, and 2-ethylhexyl esters. Methyl, ethyl, and butylacrylates are preferred. Methyl acrylate is most preferred. Vinyl estersof carboxylic acids suitable for use in the polymers include vinylesters of carboxylic acids having 2-8 carbon atoms, for example, vinylacetate, vinyl propionate, vinyl hexanoate, and vinyl 2-ethylhexanoate.Vinyl acetate is preferred. Mooney viscosities, ML 1+4 (100° C.), ofthese copolymers generally range from 1-50, preferably 1-20.Representative examples of such copolymers include terpolymers andtetrapolymers such as ethylene/methyl acrylate/methacrylic acidcopolymers; ethylene/methyl acrylate/ethyl hydrogen maleate copolymers;ethylene/acrylic acid/vinyl acetate copolymers; ethylene/butylacrylate/acrylic acid copolymers; ethylene/vinyl acetate/methacrylicacid copolymers; ethylene/fumaric acid/methyl acrylate copolymers;ethylene/methyl acrylate/carbon monoxide/methacrylic acid copolymers;and ethylene/ethyl hydrogen maleate/carbon monoxide/vinyl acetatecopolymers. Copolymer blends may also be utilized.

Another polymer type in this class of elastomeric ethylene copolymerssuitable for use in the practice of the invention contains copolymerizedunits of ethylene, an acrylic ester or vinyl ester, glycidyl acrylate ormethacrylate, and optionally, carbon monoxide. Generally, suchcompositions contain from 30-70 weight percent ethylene, 25-65 weightpercent acrylic or vinyl ester, 2-10 weight percent glycidyl acrylate ormethacrylate, and 0-15 weight percent carbon monoxide, the weightpercentages adding up to 100 weight percent. Copolymers of ethylene,acrylate ester, and glycidyl methacrylate are preferred. Representativealkyl acrylates and alkyl acrylates that are used as comonomers includemethyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate,isobutyl acrylate, and hexyl acrylate. Representative copolymers includeethylene/methyl acrylate/glycidyl methacrylate, ethylene/n-butylacrylate/glycidyl methacrylate, ethylene/vinyl acetate/glycidylmethacrylate, and ethylene/methyl acrylate/carbon monoxide/glycidylmethacrylate.

A further polymer type in this class of elastomeric ethylene copolymerssuitable for use in the practice of the invention contains copolymerizedunits of a) ethylene; b) vinyl acetate, a C₁-C₈ alkyl acrylate or aC₁-C₈ alkyl methacrylate; and c) carbon monoxide or sulfur dioxide. Thevinyl acetate, alkyl acrylate or alkyl methacrylate content of thecopolymer is generally 20-50 weight percent and the carbon monoxide orsulfur dioxide content is generally 5-40 weight percent. Examples ofsuch copolymers include ethylene/vinyl acetate/carbon monoxide;ethylene/n-butyl acrylate/carbon monoxide; ethylene/methylacrylate/carbon monoxide; ethylene/ethyl hydrogen maleate/carbonmonoxide/vinyl acetate.

Both the dipolymers and higher copolymers described above are generallyprepared by continuous copolymerization of ethylene and the comonomersin a stirred reactor in the presence of at least one free radicalinitiator at temperatures of from about 100° C. to 300° C. and atpressures of from about 130 to 350 MPa, generally as described in U.S.Pat. No. 3,883,472. Most preferably the copolymers are also prepared inthe presence of about 2-25 weight percent methanol or acetone so thatreactor fouling is decreased or eliminated.

The elastomeric component may also be selected from the class ofacrylate rubbers comprising homopolymers or copolymers of C₁-C₁₀ alkylacrylates. Preferred alkyl acrylates include ethyl acrylate, butylacrylate, and 2-ethylhexyl acrylate. Copolymeric acrylate rubberscontain copolymerized units of up to 40 weight percent monovinylmonomers, for example, styrene, acrylonitrile, vinylbutyl ether, acrylicacid, and C₁-C₁₀ alkyl acrylates different from the principal alkylacrylate comonomer. Such copolymers are available commercially, forexample, Hytemp® acrylate rubbers (acrylic homopolymer and copolymerrubbers available from Nippon Zeon, KK), and Toacron® AR-601 acrylaterubbers (polyethylacrylate polymers, available from Toa Paint, KK.).

Further, the elastomeric component may be a copolymer of a diene and anunsaturated nitrile. The diene may be, for example, butadiene. Thenitrile is preferably acrylonitrile. Such copolymers are known asnitrile rubbers and are commercially available. They generally haveacrylonitrile contents of 18-50 wt. %. Hydrogenated nitrile rubbers arealso suitable for use in the compositions of the invention.

Fluoroelastomers suitable for use as the elastomeric component of thecompositions of the invention include fluoroelastomers comprisingcopolymerized units of one or more monomers containing fluorine, such asvinylidene fluoride, hexafluoropropylene, 1-hydropentafluoropropylene,2-hydropentafluoro-propylene, tetrafluoroethylene,chlorotrifluoroethylene, and perfluoro(alkyl vinyl) ether, as well asother monomers not containing fluorine, such as ethylene, and propylene.Elastomers of this type are described in Logothetis, Chemistry ofFluorocarbon Elastomers, Prog. Polym. Sci., Vol. 14, 251-296 (1989). Thepolymers may be prepared by polymerization of the appropriate monomermixtures with the aid of a free radical generating initiator either inbulk, in solution in an inert solvent, in aqueous emulsion or in aqueoussuspension. The polymerizations may be carried out in continuous, batch,or in semi-batch processes. General preparative processes are disclosedin the Logothetis article and in U.S. Pat. Nos. 4,281,092; 3,682,872;4,035,565; 5,824,755; 5,789,509; 3,051,677; and 2,968,649.

Specific examples of such fluoroelastomers include copolymers ofvinylidene fluoride and hexafluoropropylene and, optionally,tetrafluoroethylene; copolymers of vinylidene fluoride andchlorotrifluoroethylene; copolymers of vinylidene fluoride,hexafluoropropylene, tetrafluoroethylene and chlorotrifluoroethylene;copolymers of tetrafluoroethylene and propylene; and copolymers oftetrafluoroethylene and perfluoro(alkyl vinyl) ether, preferablyperfluoro(methyl vinyl) ether. Each of the fluoroelastomers of thecomposition of the invention also comprises at least one halogenatedcure site or a reactive double bond resulting from the presence of acopolymerized unit of a non-conjugated diene. The halogenated cure sitesmay be copolymerized cure site monomers or halogen atoms that arepresent at terminal positions of the fluoroelastomer polymer chain. Thecure site monomers, reactive double bonds or halogenated end groups arecapable of reacting to form crosslinks. The cure site monomers areselected from the group consisting of brominated, chlorinated, andiodinated olefins; brominated, chlorinated, and iodinated unsaturatedethers and non-conjugated dienes.

The brominated cure site monomers may contain other halogens, preferablyfluorine. Examples are bromotrifluoroethylene,4-bromo-3,3,4,4-tetrafluorobutene-1 and others such as vinyl bromide,1-bromo-2,2-difluoroethylene, perfluoroallyl bromide,4-bromo-1,1,2-trifluorobutene, 4-bromo-1,1,3,3,4,4,-hexafluorobutene,4-bromo-3-chloro-1,1,3,4,4-pentafluorobutene,6-bromo-5,5,6,6-tetrafluorohexene, 4-bromoperfluorobutene-1 and3,3-difluoroallyl bromide. Brominated unsaturated ether cure sitemonomers useful in the invention include ethers such as2-bromo-perfluoroethyl perfluorovinyl ether and fluorinated compounds ofthe class CF₂Br—R_(f)—O—CF═CF₂, such as CF₂BrCF₂ O—CF═CF₂, andfluorovinyl ethers of the class ROCF═CFBr or ROCBr═CF₂, where R is alower alkyl group or fluoroalkyl group, such as CH₃OCF═CFBr or CF₃CH₂OCF═CFBr.

Iodinated olefins may also be used as cure site monomers. Suitableiodinated monomers include iodinated olefins of the formula:CHR═CH—Z—CH₂CHR—I, wherein R is —H or —CH₃; Z is a C₁-C₁₈(per)fluoroalkylene radical, linear or branched, optionally containingone or more ether oxygen atoms, or a (per)fluoropolyoxyalkylene radicalas disclosed in U.S. Pat. No. 5,674,959. Other examples of usefuliodinated cure site monomers are unsaturated ethers of the formula:I(CH₂CF₂CF₂)_(n)OCF═CF₂ and ICH₂CF₂O[CF(CF₃)CF₂O]_(n)CF═CF₂, and thelike, wherein n=1-3, such as disclosed in U.S. Pat. No. 5,717,036. Inaddition, suitable iodinated cure site monomers including iodoethylene,4-iodo-3,3,4,4-tetrafluorobutene-1;3-chloro-4-iodo-3,4,4-trifluorobutene;2-iodo-1,1,2,2-tetrafluoro-1-(vinyloxy)ethane;2-iodo-1-(perfluorovinyloxy)-1,1,-2,2-tetrafluoroethylene;1,1,2,3,3,3-hexafluoro-2-iodo-1-(perfluorovinyloxy)propane; 2-iodoethylvinyl ether; 3,3,4,5,5,5-hexafluoro-4-iodopentene; andiodotrifluoroethylene are disclosed in U.S. Pat. No. 4,694,045.

Examples of non-conjugated diene cure site monomers include1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene and others, such as thosedisclosed in Canadian Patent 2,067,891. A suitable triene is8-methyl-4-ethylidene-1,7-octadiene.

Of the cure site monomers listed above, preferred compounds include4-bromo-3,3,4,4-tetrafluorobutene-1,4-iodo-3,3,4,4-tetrafluorobutene-1,and bromotrifluoroethylene.

Additionally, or alternatively, iodine, bromine or mixtures thereof maybe present at the fluoroelastomer chain ends as a result of the use ofchain transfer or molecular weight regulating agents during preparationof the fluoroelastomers. Such agents include iodine-containing compoundsthat result in bound iodine at one or both ends of the polymermolecules. Methylene iodide; 1,4-diiodoperfluoro-n-butane; and1,6-diiodo-3,3,4,4,tetrafluorohexane are representative of such agents.Other iodinated chain transfer agents include1,3-diiodoperfluoropropane; 1,4-diiodoperfluorobutane;1,6-diiodoperfluorohexane; 1,3-diiodo-2-chloroperfluoropropane;1,2-di(iododifluoromethyl)-perfluorocyclobutane;monoiodoperfluoroethane; monoiodoperfluorobutane;2-iodo-1-hydroperfluoroethane, etc. Particularly preferred arediiodinated chain transfer agents. Examples of brominated chain transferagents include 1-bromo-2-iodoperfluoroethane;1-bromo-3-iodoperfluoropropane; 1-iodo-2-bromo-1,1-difluoroethane andothers such as disclosed in U.S. Pat. No. 5,151,492.

Copolymers of ethylene, tetrafluoroethylene, perfluoro(alkyl vinyl)ether and a bromine-containing cure site monomer, such as thosedisclosed by Moore, in U.S. Pat. No. 4,694,045 are suitable for use inthe present invention. Copolymers of tetrafluoroethylene andperfluoro(alkyl vinyl) ether commonly containing fluorinated nitrilecure sites, for example perfluoro(8-cyano-5-methyl-3,6-dioxa-1-octene)and others disclosed in U.S. Pat. No. 4,983,697 may also be used. Otheruseful fluoroelastomers containing brominated or iodinated olefin curesite monomers are described in U.S. Pat. Nos. 4,035,565; 4,564,662;4,745,165; 4,694,045; 4,948,852; and 4,973,633.

Each of these classes of copolymers includes dipolymers or higher ordercopolymers having copolymerized units of other comonomers.

It has been found that raw fluoroelastomers having Mooney viscosities inthe range of 5-150, ML 1+4 (121° C.), preferably 10-70, ML 1+4 (121° C.)are particularly useful in the compositions of the present invention.Those compositions wherein the fluoroelastomer has a Mooney viscositywithin the preferred range exhibit an optimum balance of processabilityand tensile properties.

It has also been found that compositions containing fluoroelastomershaving levels of copolymerized cure site monomer units within the rangeof 0.05-10.0 wt. %. exhibit enhanced cure state.

Chlorinated olefin polymers are also suitable for use as the elastomericcomponent of the compositions of the invention. The chlorinated olefinpolymers also specifically include chlorosulfonated olefin polymers. Byolefin polymers is meant homopolymers and copolymers of C₂-C₈alpha-monoolefins, including graft copolymers. The copolymers may bedipolymers or higher order copolymers, such as terpolymers ortetrapolymers. The olefin polymers may be branched or unbranched and maybe prepared by free radical processes, Ziegler-Natta catalysis orcatalysis with metallocene catalyst systems. for example those disclosedin U.S. Pat. Nos. 5,272,236 and 5,278,272. Particularly useful examplesof olefin polymers include homopolymers of C₂-C₃ alpha monoolefins,copolymers of ethylene and carbon monoxide, and copolymers of ethyleneand at least one ethylenically unsaturated monomer selected from thegroup consisting of C₃-C₂₀ alpha monoolefins, C₁-C₁₂ alkyl esters ofunsaturated C₃-C₂₀ monocarboxylic acids, unsaturated C₃-C₂₀ mono- ordicarboxylic acids, anhydrides of unsaturated C₄-C₈ dicarboxylic acids,and vinyl esters of saturated C₂-C₁₈ carboxylic acids. Specific examplesof these polymers include polyethylene, polypropylene, ethylene vinylacetate copolymers, ethylene acrylic acid copolymers, ethylenemethacrylic acid copolymers, ethylene methyl acrylate copolymers,ethylene methyl methacrylate copolymers, ethylene n-butyl methacrylatecopolymers, ethylene glycidyl methacrylate copolymers, graft copolymersof ethylene and maleic anhydride, graft copolymers of propylene andmaleic anhydride, and copolymers of ethylene with propylene, butene,3-methyl-1-pentene, hexene, or octene. Preferred olefin polymers arepolyethylene, ethylene propylene copolymers, ethylene butene copolymers,ethylene octene copolymers, copolymers of ethylene and acrylic acid,copolymers of ethylene and methacrylic acid, and copolymers of ethyleneand vinyl acetate. The olefin polymers have number average molecularweights within the range of 1,000 to 300,000, preferably from 50,000 to300,000. The chlorinated and chlorosulfonated olefin polymers havechlorine contents of from about 15 weight percent to about 70 weightpercent. The chlorosulfonated olefin polymers have sulfur contents of0.5-10 weight percent, preferably 1-3 weight percent.

The chlorinated or chlorosulfonated olefin polymers may be prepared fromthe olefin polymers by free radical initiated chlorination andchlorosulfonation. Chlorination of the olefin polymers may take place attemperatures of 50° C.-150° C. and at pressures of 1-10 atmospheresusing gaseous chlorine as the chlorinating agent. In solutionchlorination, the reaction medium is an inert solvent, for examplecarbon tetrachloride, chlorinated benzene, chloroform or fluorobenzene.Alternatively, slurry chlorination in aqueous or organic suspension canbe used. Fluidized bed processes are also known, as well as meltprocesses. Chlorosulfonation of the olefin polymer starting materialsmay take place in solution, under similar conditions, utilizing gaseouschlorine and sulfur dioxide, sulfuryl chloride, or a combination ofchlorine, sulfur dioxide and sulfuryl chloride. Commercially availablechlorinated and chlorosulfonated olefin polymers include Tyrin®chlorinated polyethylene, Hypalon® chlorosulfonated polyethylene, andAcsium® chlorosulfonated polyethylene, all available from DuPont DowElastomers L.L.C.

Epichlorohydrin elastomers that are suitable for use as the elastomericcomponent of the compositions of the invention include bothpolyepichlorohydrin homopolymers and copolymers comprising copolymerizedunits of epichlorohydrin and ethylene oxide. Terpolymers containing curesite monomers, such as allyl glycidyl ether, may also be used. Suchcompositions generally contain about 20-45 wt. % chlorine. Commerciallyavailable examples include Epichlomer® rubber manufactured by DaisoEpichlo Rubber Co., Ltd., Japan and Hydrin® epichlorohydrin rubbermanufactured by Nippon Zeon Co., Ltd., Japan.

The elastomeric component of the compositions of the invention may be ablend of elastomers as well as a single elastomer. The blends may bemixtures of polymers of the same class, for example, a brominatedfluoroelastomer and an iodinated fluoroelastomer, or they may bemixtures of more than one type of elastomer, for example a chlorinatedpolyolefin rubber and an ethylene copolymer rubber. Blends wherein onlyone elastomer is capable of cure by exposure to UV radiation are alsocontemplated by the invention. Blend compositions would be particularlyuseful for balancing physical properties. For example, it would bedesirable to balance state of cure with fuel resistance by blendingfluoroelastomers with epichlorohydrin rubbers. In other circumstances,blends of costly polymers with less expensive polymers often yield acombination of properties that are adequate for less demandingapplications. In this context, blends of fluoroelastomers and nitrilerubber or fluoroelastomers and ethylene acrylate copolymer elastomerswould be suitable for use as the elastomeric component of thecompositions of the invention. The Mooney viscosities of the blends willpreferably be within the range of 1-150 because within this range theblends will be suitable for use in the process of the present inventionfor producing general rubber articles, such as seals.

In addition to an elastomeric component, the curable compositions of theinvention also include at least one multifunctional crosslinking agent.Preferably the multifunctional crosslinking agent will be an acrylic ormethacrylic crosslinking agent. In addition, it may be a multifunctionalcyanurate or multifunctional isocyanurate, such as triallyl isocyanurateor triallyl cyanurate. By multifunctional acrylic or methacryliccrosslinking agent is meant an ester that is a reaction product of apolyhydroxylic compound, generally a polyhydroxylic alcohol, and acrylicacid or methacrylic acid, wherein the crosslinking agent has at leasttwo carbon-carbon double bonds. Such compositions are commonly referredto in the art as multifunctional acrylates or multifunctionalmethacrylates. Typical multifunctional acrylates and methacrylates havemolecular weights of 150 to 1,000 and contain at least two polymerizableunsaturated groups per molecule.

Representative multifunctional acrylic crosslinking agents includeacrylates and methacrylates such as ethylene glycol diacrylate; ethyleneglycol dimethacrylate; 1,6-hexanediol diacrylate; 1,6-hexanedioldimethacrylate; 1,4-butanediol diacrylate; pentaerythritol triacrylate;pentaerythritol tetraacrylate; dipentaerythritol pentaacrylate,methoxy-1,6-hexanediolpentaerythritol triacrylate; trimethylolpropanetriacrylate; tetraethylene glycol diacrylate; polymethacrylateurethanes; epoxy acrylates; polyester acrylate monomers and oligomers;trimethylolpropane propoxylate triacrylate; poly-n-butyleneoxide glycoldiacrylates; and bisphenol A alkylene oxide adduct diacrylates.Trimethylolpropane triacrylate and trimethylolpropane trimethacrylateare preferred crosslinking agents because these compounds are readilyavailable. In addition, compression set and crosslink density areenhanced in compositions containing these crosslinking agents comparedto compositions containing difunctional acrylates, such as diethyleneglycol dimethacrylate.

The multifunctional acrylic and methacrylic crosslinking agents arecapable of homopolymerization when irradiated. Thus, when the curablecompositions of the invention that contain multifunctional acrylates ormethacrylates are exposed to UV radiation, two reactions occursimultaneously. The multifunctional crosslinking agent reacts with theelastomeric polymer component to form interchain and intrachaincrosslinks, resulting in a rubber matrix. In addition, excessmultifunctional crosslinking agent will homopolymerize and form aninterpenetrating network which acts to reinforce the rubber matrix, muchin the same manner as fillers reinforce elastomers. It is thereforepossible to control the hardness of the final cured product by adjustingthe proportion of multifunctional crosslinker present in the curablecomposition. In general, difunctional acrylates and methacrylates areless efficient crosslinking agents compared to their analogues havinghigher functionalities. Consequently, crosslinking agents of the classhaving higher functionalities are preferred for purposes of the presentinvention.

Elastomeric materials compounded and cured according to methods commonlyused in rubber processing technology generally contain carbon black ormineral fillers as reinforcing agents. Reinforcement is reflected inproperties such as hardness, modulus, and tensile strength. Generally,reinforced elastomers are characterized by non-linear stress/straindependence. In contrast, non-reinforced elastomer compositions arecharacterized by an initial stress build-up at low deformation whichdoes not substantially increase at higher deformation. Further,non-reinforced elastomer compositions tend to break at relatively lowultimate tensile strength.

Use of fillers in UV-initiated reactions would normally be expected tointerfere with the UV curing process. However, the present processpermits curing of translucent compositions. Thus, the compositions ofthe present invention may contain a limited amount of fillers, generallyno more than 15 parts by weight per 100 parts polymer. Reinforcement iseffected simultaneously with crosslinking by formation of aninterpenetrating network. The resultant product exhibits stress/strainbehavior that is more linear than that of traditional elastomers whichcontain fillers which are not chemically bound to the elastomer matrix.

The amount of multifunctional crosslinking agent present in thecompositions of the invention will depend on the particular elastomerused. Generally, the amount ranges from 0.5 to 25 weight percent, basedon the combined weight of polymer, multifunctional crosslinking agent,and UV initiator.

The third component of the curable compositions of the invention is a UVinitiator. It may be selected from those organic chemical compoundsconventionally employed to promote UV-initiated formation of radicalseither by intramolecular homolytic bond cleavage or by intermolecularhydrogen abstraction. Such agents include organic compounds having arylcarbonyl or tertiary amino groups. Among the compounds suitable for useare benzophenone; acetophenone; benzil; benzaldehyde;o-chlorobenzaldehyde; xanthone; thioxanthone; 9,10-anthraquinone;1-hydroxycyclohexyl phenyl ketone; 2,2-diethoxyacetophenone;dimethoxyphenylacetophenone; methyl diethanolamine;dimethylaminobenzoate; 2-hydroxy-2-methyl-1-phenylpropane-1-one;2,2-di-sec-butoxyacetophenone; 2,2-dimethoxy-1,2-diphenylethan-1-one;benzil dimethoxyketal; benzoin methyl ether; and phenyl glyoxal. Uponexposure to UV radiation, a variety of photochemical transformations mayoccur, for example, the UV initiator may form free radical reactivefragments that react with the acrylate end groups of the multifunctionalacrylic or methacrylic crosslinking agent. This initiates crosslinkingof the polymer as well as homopolymerization of the acrylic ormethacrylic crosslinking agent. A preferred UV initiator is1-hydroxycyclohexyl phenyl ketone because of the rapidity with which itgenerates free radicals when exposed to UV radiation. Mixtures of UVinitiators may also be used. This is often desirable because it providesmore efficient production of radicals in certain cases. In general, theUV initiator will be present in an amount of 0.1 to 10.0 weight percent,based on the total weight of polymer, multifunctional crosslinkingagent, and UV initiator. However, it is preferable to use between0.5-2.5 weight percent UV initiator, most preferably 0.5-1.0 weightpercent UV initiator, based on total weight of polymer, crosslinkingagent and UV initiator, because high levels of photoinitiator tend tointerfere with penetration and do not substantially contribute to theoverall crosslink density. Within the ranges disclosed herein, there isan optimum level of photoinitiator for each particular combination ofuncured gum elastomer and crosslinking agent. These optimum levels canbe readily determined by one skilled in the art. For example,hydrogenated nitrile rubber will generally require a higher level ofphotoinitiator than a copolymer of ethylene, methyl acrylate, and ethylhydrogen maleate. Higher levels of photoinitiator increase the crosslinkdensity at the surface of the cured composition. Low levels ofphotoinitiators can result in better (i.e. lower) compression sets ofsamples that are several millimeters thick.

In addition, for purposes of the present invention, the processingtemperature must not exceed the temperature at which thermal degradationof the UV initiator occurs. In some cases such degradation would resultin scorchy compositions due to formation of free radicals. This is sobecause thermally-induced fragmentation of the initiator within theprocessing equipment results in premature crosslinking of the elastomer.In other instances, slow curing compositions would result due toinactivation of the initiator. Degradation temperatures will differ foreach particular UV initiator. Depending upon the type of rubber and theamount of additives, the processing temperature will range from between25° and 250° C. It is an object of the invention to provide stableelastomeric compositions which can be applied to a substrate attemperatures of up to 250° C. A further practical limitation on theprocessing temperature is that the temperature must not exceed thesoftening point of the substrate to which it is applied.

The elastomeric component, multifunctional crosslinking agent component,and UV initiator component are present in the compositions of thepresent invention in specific relative ratios. When the elastomericcomponent of the composition is an ethylene copolymer elastomer anacrylate rubber or a nitrile rubber, the elastomer is present in anamount of 75-95 weight percent, based on the total weight of elastomer,crosslinking agent, and UV initiator. The multifunctional crosslinkingagent is present in an amount of 2 to 24 weight percent, based on thetotal weight of elastomer, crosslinking agent, and UV initiator.Finally, the UV initiator is present in an amount of 0.2 to 5.0 weightpercent based on the total weight of elastomer, crosslinking agent, andUV initiator. Preferably, the elastomeric component will be present inan amount of from 87-95 weight percent, based on the total weight ofelastomer, crosslinking agent, and UV initiator. The level ofcrosslinker determines compression set resistance and hardness in thecurable composition of the invention. If less than 2 weight percentcrosslinker is present, a composition having low hardness and poorcompression set resistance is formed. Greater than 30 weight percentcrosslinker results in production of a composition of hardness greaterthan 70 Shore A. Such compositions are generally unsuitable for use insealing, especially gasketing, applications. The particular componentrange selected will thus depend on the specific end use contemplated.Preferred compositions contain 5-20 weight percent multifunctionalcrosslinking agent, and most preferred compositions contain 5-15 weightpercent multifunctional crosslinking agent, based on the combined weightof polymer, multifunctional crosslinking agent and UV initiator.

When the elastomeric component of the composition is a fluoroelastomer,the elastomer is present in an amount of 70-99 weight percent, based onthe total weight of elastomer, crosslinking agent, and UV initiator. Themultifunctional crosslinking agent is present in an amount of 0.5-20weight percent, based on the total weight of elastomer, crosslinkingagent, and UV initiator. Finally, the UV initiator is present in anamount of 0.1-10 weight percent based on the total weight of elastomer,crosslinking agent, and UV initiator. Preferably, the elastomericcomponent will be present in an amount of from 75-95 weight percent,based on the total weight of elastomer, crosslinking agent, and UVinitiator. The level of crosslinker determines compression setresistance and hardness in the curable composition of the invention.Preferably the multifunctional crosslinker is present in an amount of4-15 weight percent based on the weight of elastomer, crosslinker and UVinitiator. If less than about 4 weight percent crosslinker is present, acomposition having fairly low hardness and relatively high compressionset resistance is formed. Greater than about 15 weight percentcrosslinker results in unacceptably high modulus, very low elongation atbreak, and poor compressability of the cured composition. Suchcompositions are generally unsuitable for use in sealing, especiallygasketing, applications. The particular component range selected willthus depend on the specific end use contemplated.

When chlorinated olefin polymers, chlorosulfonated olefin polymers orepichlorohydrin rubbers are used as the elastomeric component of thecomposition, the elastomer is present in an amount of 80-97 weightpercent, based on the total weight of elastomer, crosslinking agent, andUV initiator. The multifunctional crosslinking agent is present in anamount of 2-19.5 weight percent, based on the total weight of elastomer,crosslinking agent, and UV initiator. The UV initiator is present in anamount of 0.2-5.0 weight percent based on the total weight of elastomer,crosslinking agent, and UV initiator. Preferably, the elastomericcomponent will be present in an amount of from 85-95 weight percent,based on the total weight of elastomer, crosslinking agent, and UVinitiator. Preferably, the crosslinker will be present in an amount of3-15 weight percent, based on the total weight of elastomer,crosslinking agnet and UV initiator. If less than 3 weight percentcrosslinker is present, a cured composition having relatively highcompression set generally results. Greater than 15 weight percentcrosslinker results in a high level of hompolymerized acrylic ormethacrylic crosslinker producing a highly crosslinked elastomericmatrix of high hardness, low compressability and low elongation atbreak. As with the other compositions of the invention, the particularcomponent range selected will thus depend on the specific end usecontemplated.

Various additives, commonly used in rubber compounding may beincorporated into the compositions of the present invention to modify,stabilize, and reinforce them. Preferably, such additives will be usedin amounts which do not interfere substantially with the crosslinkingreaction of the uncured polymeric component. For example, if largeamounts of fillers that are opaque to UV light are utilized, the filledcompositions will not cure evenly throughout, or only the surface of thecomposition will be cured. Usually, fillers may be employed in amountsof up to about 15 parts per hundred parts of elastomer. Typical examplesinclude non-black fillers such as minerals or glass fibers. Polymericfillers of high reinforcing efficiency, such as polytetrafluoroethyleneand aramid fibers, may also be used, generally at low levels. It ispreferable that the presence of additives does not raise the viscosityof the curable composition used in the process of the invention to morethan ML 1+4 (100° C.) of 150 or lower it to less than ML 1+4 (100° C.)of 1. Compositions outside this range are not suitable for the gasketingin place process of the invention.

When the polymeric component is a fluoroelastomer, preferred curablecompositions of the present invention will include 0.01-2.0 parts byweight per hundred parts by weight fluoroelastomer of an organotinhydride. Compositions wherein this additive is present exhibit excellentcure profiles. That is, the cure rate increases rapidly after initiationand the cure state remains high throughout the cure process. Preferably0.1-1 parts by weight of the organotin hydride will be used per 100parts by weight fluoroelastomer. Tri-n-butyltin hydride is preferred.

When ethylene acrylate copolymers are utilized as the polymericcomponent, heat and oxidation resistance of the compositions of theinvention are preferably enhanced by incorporation of antioxidants.Generally, aromatic antioxidants are utilized, especially aromaticamines. Due to their protective action, these compounds interfere to acertain extent with the free radical crosslinking reaction initiated byUV radiation. In the absence of antioxidants, the compositions aresubject to surface cracking when exposed to temperatures of 150° C. forperiods of several days. Among the most useful antioxidants are4,4′-bis(α, α-dimethyl-benzyl) diphenylamine and blends of 4,4′-bis(α,α-dimethylbenzyl)diphenylamine with 4-(α,α-dimethylbenzyl)diphenylamine. Hindered phenols may be employed, butthey interfere more with the curing reaction than do the aromaticamines. Antioxidants are usually incorporated at a level of between0.5-2 parts per 100 parts polymer. Other additives may also beincorporated into the compositions of the invention, for exampleplasticizers, adhesion promoters, flame retardants, and process aidscommonly used in rubber compounding.

Small amounts of inhibitors may also be present in the compositions ofthe invention as a result of the presence of these additives incommercial samples of acrylic or methacrylic crosslinking agents. Theinhibitors are generally present in low amounts, for example below 1500ppm (parts per million, based on the weight of the crosslinking agent).They act to prevent thermally induced polymerization of the crosslinkingagents during storage and shipment.

The compositions of the invention are particularly suited formanufacture of elastomeric seals and gaskets in situ using a techniquewe refer to herein as gasketing in place. According to this technique, acurable elastomeric composition is heated to a temperature of 25°-250°C., preferably 90° C.-170° C. The heated composition is then meteredonto a substrate to form an uncured seal of a desired thickness which isthen cured. Thus, the seal is formed in place directly on the object tobe sealed, rather than in a separate molding step. Typically, uncuredseals are formed in thicknesses of 1-15 mm, preferably in thicknesses of2-8 mm.

Robotized hot melt equipment may be used to apply gaskets in place. Inone embodiment of the process of the present invention, a curablecomposition comprising a low viscosity elastomer component,multifunctional crosslinking agent, and UV initiator, is introduced to adrum having a heated platen and piston. The composition, when heated,becomes soft and extrudable. It is forced out of the drum by the actionof the piston, generally at relatively low pressures, typically lessthan 5.0 bars (i.e. 0.5 MPa). The composition is then fed by gear orpiston pumping through heated tubing to an application gun fitted to amultidimensional industrial robot capable of precise and rapid metering.In this way, the composition can be introduced into a groove of a partsuch as a thermoplastic article that has just been produced, for exampleby molding. The bead of uncured elastomer in the groove solidifiesrapidly as it cools and forms an uncured sealing element. The groove canbe in a part made from other materials as well, including but notlimited to metal. Alternatively, the composition can be deposited ontothe exterior of an object to form a seal. This hot melt applicationmethod is preferred for low viscosity elastomers, generally of Mooneyviscosity 1-20 ML 1+4 (100° C.), especially ethylene acrylic elastomers,polyacrylate rubbers, nitrile rubbers, or ethylene vinyl acetateelastomers. The method permits extrusion from a drum using relativelylow pressures. Continuous feeding and metering pumps are capable ofhandling compositions of the invention having viscosities up to 1000Pa.s. Hot melt equipment may be used for compositions having somewhathigher viscosities, for example ML 1+4 (100° C.) of 70, by employing anextruder to introduce the composition into the heated tubing. Theviscosity thereupon decreases, permitting formation of seals from thehigher viscosity compositions.

In another embodiment of the process of the invention, relatively highviscosity compositions or compositions of relatively low heat resistancemay be formed into uncured seals by the gasketing in place technique.Instead of using hot melt equipment, screw extruders are exclusivelyutilized to deliver the elastomeric composition to the article to besealed. This technique is particularly useful when fluoroelastomers andchlorinated elastomers of Mooney viscosity 10-90 [ML 1+10 (121° C.)] areemployed as the elastomeric component of the invention. An extruder thatis used in combination with a flexible arm to apply a bead of uncuredelastomer to a groove is particularly preferred for such gasketing inplace processes. This differs from conventional extruder technology inthat the extruder is not utilized to form the finished part. Instead, itpumps the uncured elastomer composition to a robotized application headthat meters the composition and deposits it at the location to besealed. Use of screw extruders results in relatively high energy inputto the polymer compared with processes which utilize hot melt equipment.In order to minimize elastomer degradation in the extruder, theextrusion process must not cause the temperature of the compound to riseabove 250° C. This generally requires slow extrusion speeds.Consequently, extrusion processes are generally slower methods ofmanufacture. Further, such equipment requires high investment costs.Those skilled in the art will recognize that the appropriate temperaturefor extrusion will be dependent on the viscosity of the uncuredelastomer, the molecular weight of the uncured elastomer, the level ofcrosslinking agent, the decomposition temperature of the photoinitiatorand the volatilization temperature of the crosslinking agent and willselect a value within the range of 25°-250° C. that is optimum for theparticular circumstances.

The gasketing process of the present invention may be employed formanufacture of seals and gaskets using the compositions of the presentinvention or other curable elastomer compositions. Generally, theelastomer component will be present in an amount of from 70-99 parts byweight, the multifunctional crosslinker will be present in an amount of0.1-10 parts by weight, and the UV initiator will be present in anamount of 0.1-10 parts by weight, all based on the combined weight ofelastomer, crosslinker, and UV initiator. For example, the processes maybe used to form gaskets from fluoroelastomer compositions comprising afluoroelastomer, multifunctional crosslinker and UV initiator whereinthe fluoroelastomer component of the composition does not contain acopolymerized brominated, iodinated, chlorinated or non-conjugated dienecure site monomer or iodinated or brominated polymer end groups. Suchcopolymers are commercially available and include dipolymers ofvinylidene fluoride with hexafluoropropylene; terpolymers of vinylidenefluoride, hexafluoropropylene, and tetrafluoroethylene; and copolymersof tetrafluoroethylene and propylene. In addition, ethylene alpha-olefinelastomers, such as elastomeric copolymers and interpolymers of ethylenewith one or more comonomers selected from propylene, 1-butene, 1-hexene,1-octene, 4-methyl-1-penetene, and other C₃-C₂₀ alpha-olefins, aresuitable elastomeric components in the UV curable composition.Elastomeric copolymers of ethylene, a C₃-C₈ olefin, and a diene may alsobe used in the process of the invention. These copolymers can beterpolymers, tetrapolymers or higher order copolymer elastomers of theethylene/C₃-C₈ alpha olefin/diene type. These elastomers are copolymersof ethylene, a C₃-C₈ alpha-olefin and at least one non-conjugated diene.They may, in addition, contain a minor amount, generally up to 10 weightpercent, of at least one other diene or triene having copolymerizabledouble bonds. Preferred C₃-C₈ alpha-olefins are propylene and butene.The non-conjugated dienes of the first type include 1,4-hexadiene;2-methyl-1,5-hexadiene; vinyl norbornene;8-methyl-4-ethylidene-1,7-octadiene; 1,9-octadecadiene;dicyclopentadiene; tricyclopentadiene; 5-ethylidene-2-norbornene; or5-methylene-2-norbornene. Preferred dienes having one reactive doublebond are 1,4-hexadiene, dicyclopentadiene and ethylidene norbornene. Thenon-conjugated dienes of the second type include norbornadiene;1,4-pentadiene; 1,5-hexadiene; 1,7-octadiene; 1,2-heneicosadiene; or5-(5-hexenyl)-2-norbornene, preferably norbornadiene. These polymers aregenerally produced by polymerization in the presence of Ziegler-Nattacatalysts or by polymerization in the presence of metallocene catalysts.Preparative techniques for ethylene alpha-olefin elastomers prepared inthe presence of metallocene catalysts may be found in U.S. Pat. Nos.5,278,272 and 5,272,236. Typical ethylene alpha-olefin copolymers andEPDM elastomers are commercially available as Engage® polyolefinelastomers and Nordel® hydrocarbon rubbers from DuPont Dow ElastomersL.L.C. The proportion of elastomer, multifunctional crosslinking agent,and UV initiator will generally be in the weight ratio of70-99:0.5-19.5:01-10, respectively, when the elastomer is afluoroelastomer and 80-98:1-20:0.2-5.0, respectively, when the elastomeris an ethylene alpha-olefin elastomer or an EPDM elastomer.

In order to optimize the elastomeric properties of seals made by theabove-described processes, they must be crosslinked, i.e. cured. Itwould be impractical to utilize a heat-activated cure system toaccomplish a rapid crosslinking reaction in such processes. One wouldrisk converting the curable composition used to form the seals to anintractable, crosslinked material during the metering step.Specifically, as the curable composition was heated or subjected totemperature elevation caused by mechanical working, the crosslinkingreaction would be triggered. It would be difficult to control prematuregelling (i.e. scorch) during metering. Because crosslinked compositionsdo not flow readily, processes which result in scorchy products areundesirable. Consequently, heterolytic cure systems, which rely onthermally-induced crosslinking reactions, are not appropriate for thepresent process. In addition, the most common homolytic, i.e. freeradical, curing processes, which depend on thermal decomposition ofperoxides, are also unsuitable for use in the present process. It has,however, been found that curable composition using the process of theinvention can be effectively cured by UV induced free radical processes.

UV cure of elastomeric compositions using the process of the inventionmay be accomplished at room temperature or at higher temperatures. Forexample, in certain circumstances wherein the elastomeric composition isto be used as a sealant, it may be desirable to perform a photocureimmediately after application of the uncured composition to the objectto be sealed. At that point, the temperature of the composition may beas high as 250° C. However, heating the curable composition is neithernecessary nor particularly desirable for an effective photocure. Inaddition, when the compositions are used to form seals by the gasketingin place technique on thermoplastic articles, low temperature cureminimizes any possibility of degradation or thermal distortion of thethermoplastic. Further, it is not necessary to perform the UVirradiation in an inert atmosphere. The cure reaction can be conductedunder atmospheric conditions with no deleterious effects. In addition,it has also been found that in some cases, particularly when curingchlorinated or chlorosulfonated polyolefins, curing the compositionunder water is preferable to minimize heat buildup. This minimizes thetendency of these polymers to dehydrochlorinate, a process that causespolymer degradation and discoloration and which inhibits UV cure.

For purposes of the process of this invention, the wavelength spectrumof radiation used to effect the curing reaction typically corresponds tothe absorption maximum of the UV initiator. This typically ranges fromabout 200-400 nanometers. Suitable UV radiation sources include mediumpressure mercury vapor lamps, electrodeless lamps, pulsed xenon lamps,and hybrid xenon/mercury vapor lamps. A preferred arrangement comprisesone or more lamps together with a reflector, which diffuses theradiation evenly over the surface to be irradiated. The radiation dosagemust be sufficient to cure the polymeric composition, i.e. to produce acured composition having a compression set of 90 or lower, preferably 50or lower, and an elongation at break of at least 100%. A dosage of atleast about 10 joules per square centimeter, and preferably 20 joules isusually sufficient for optimum cure. Dosage is a function of the time ofexposure to the UV radiation, the distance from the UV radiation sourceand the power level of the radiation source. The required radiation dosecan be readily determined by curing small samples of the curablecomposition and measuring physical properties, such as tensile strength,compression set and elongation, after cure. In most instances, anacceptable degree of cure can be obtained by exposures of 30-300 secondsusing a lampt of about 80 W/cm. Appropriate adjustments may be madedepending on the power of the lamp, distribution of the output over theUV range, the thickness of the sample as well as the polymericcomponent, level of crosslinking agent present, and level of fillerpresent. For example, ethylene acrylate copolymer rubber containingfiller would require a longer cure time than the same compositionwithout filler.

Foaming agents may be incorporated into the curable compositions of thepresent invention. In such circumstances a cellular structure will beformed by exposure of the curable composition to UV radiation as aresult of thermal decomposition of the foaming agent induced bysimultaneous heating that occurs during exposure to UV light. Thisheating phenomenon may be augmented and controlled by additionalexternal application of heat. Typical foaming agents that may beemployed include p,p′-oxybisbenzenesulfonyl hydrazide,azodicarbon-amides, p-toluenesulfonyl semicarbazides, anddinitrosopentamethylene tetramine. Alternatively, the UV curing reactionmay also be accomplished with cooling, so that curing and foaming occursequentially, rather than simultaneously. That is, the curablecomposition is exposed to UV radiation with cooling, and the curedcomposition is then passed through a hot air tunnel to cause foaming.Closed cell structures of low specific gravity may be prepared by suchprocesses. For example, structures with specific gravities of 0.3 g/cm³may be obtained.

Low viscosity compositions of the invention may be utilized as coatingcompositions for solvent-free systems or systems having low levels, i.e.up to about 2 wt. % of solvent, based on the total weight of elastomer,multifunctional crosslinker and UV initiator. It is thus not necessaryto cast films from polymer solutions. Instead, the low viscosity curablecomposition flows onto the substrate by application of heat. The optimumratio of elastomer, multifunctional crosslinking agent and UV initiatorfor coating compositions will be different from that of compositionsuseful in the manufacture of seals and gaskets. For example, arelatively thin coating will cure more quickly and permit use ofrelatviely high levels of UV initiator because opacity will not be aproblem. In addition, higher levels of multifunctional crosslinkingagents may be employed to reduce viscosity and permit easier processingbecause coating compositions can tolerate higher hardness than gasketingmaterials. Further, coating compositions do not require the compressionset resistance that is necessary for seals and gaskets.

The curable elastomeric compositions of the present invention are usefulin manufacture of general rubber goods, coating compositions, foams andwire coating. They are most advantageously used however, in preparationof seals and gaskets for thermoplastic articles, particularly thoseemployed in automotive applications.

The invention is illustrated by the following specific embodimentswherein all parts are by weight unless otherwise indicated.

EXAMPLES Example 1

A curable elastomeric composition of the invention was prepared bymixing on a rubber mill 92.5 parts of a copolymer of ethylene and methylacrylate (ethylene content 34 wt. %, Mooney viscosity ML1+4 (100° C.) of8), 7.5 parts trimethylolpropane triacrylate, 0.75 parts Irgacure® 1800photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexyl phenyl ketoneand 25 wt. % bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphineoxide, available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445antioxidant (4,4′-di(α, α-dimethyl-benzyl)diphenylamine, available fromUniroyal, Inc.). Uncured slabs of 6 mm thickness were shaped by moldingin a mold coated with Teflon® fluoropolymer resin. The slabs wereexposed for one and two minutes respectively to UV radiation from amedium pressure mercury lamp which emitted radiation of wavelengthapproximately 250-400 nm at 80 watts/cm. The distance of the samplesfrom the lamp was 10 cm. The cured samples exhibited the propertiesshown in Table I.

TABLE I Length of Exposure (Minutes)  1  2 Hardness, Shore A 46 50Surface Facing Source Hardness, Shore A 35 42 Surface Away From Source

Example 2

A curable elastomeric composition of the invention was prepared bymixing on a rubber mill 92.5 parts of an acrylate rubber (ethyl acrylatehomopolymer, Mooney viscosity ML1+4 (100° C.) of 36, available fromNippon Zeon KK), 7.5 parts trimethylolpropane triacrylate, 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethyl-benzyl)-diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 6 mm thickness were shaped by molding in a moldcoated with Teflon® fluoropolymer resin. The slabs were exposed for oneand two minutes respectively to UV radiation from a medium pressuremercury lamp which emitted radiation of wavelength approximately 250-400nm at 80 watts/cm. Cure was effected on samples placed 10 cm from thelamp. The cured samples exhibited the properties shown in Table II.

TABLE II Length of Exposure (Minutes)  1  2 Hardness, Shore A 34 45Surface Facing Source Hardness, Shore A 25 30 Surface Away From Source

Example 3

A curable elastomeric composition of the invention was prepared bymixing on a rubber mill 92.5 parts of a copolymer of ethylene and vinylacetate (ethylene content 32 wt. %, Mooney viscosity ML1+4 (100° C.) of9), 7.5 parts trimethylolpropane triacrylate, 0.75 parts Irgacure® 1800photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexyl phenyl ketoneand 25 wt. % bis(2,6-dimethoxy-benzoyl)-2,4,4-trimethylphenylphosphineoxide, available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445parts antioxidant (4,4′-di(α, α-dimethyl-benzyl)diphenylamine, availablefrom Uniroyal, Inc.). Uncured slabs of 6 mm thickness were shaped bymolding in a mold coated with Teflon® fluoropolymer resin. Samples ofthe rubber sheet were exposed for two minutes respectively to UVradiation from a medium pressure mercury lamp, which emitted radiationof from about 250 nm to 400 nm at 80 watts/cm. The distance of thesamples from the lamp during the curing process was 10 cm. The curedsamples exhibited the properties shown in Table III.

TABLE III Length of Exposure (Minutes)  2 Hardness, Shore A 45 SurfaceFacing Source Hardness, Shore A 36 Surface Away From Source

Example 4

Three curable compositions of the present invention, Samples 4A, 4B, and4C, were prepared by mixing on a rubber mill 85 parts of a copolymer ofethylene and methyl acrylate (ethylene content 34 wt. %, Mooneyviscosity ML1+4 (100° C.) of 8) and the components shown in Table IV.Uncured slabs of 6 mm thickness were shaped by molding in a mold coatedwith Teflon® fluoropolymer resin. The resultant polymer slabs wereexposed for 4 minutes to UV radiation from a medium pressure mercurylamp, which emitted radiation of wavelength approximately 300-400 nm ata power of 80 W/cm. Exposure of the samples was at a distance of 10 cmfrom the lamp. Shore A hardness of the surface exposed to the lamp andthe surface facing away from the lamp were determined for the 6 mmspecimens. In addition, compression set of the cured compositions wasdetermined according to ISO 815 on specimens died out of the 6 mm slabs.Results are shown in Table IV.

TABLE IV Sample Composition 4A 4B 4C Polymer (parts) 85 85 85Trimethylolpropane triacrylate 15 — — Trimethylolpropane trimethacrylate— 15 — Diethyleneglycol dimethacrylate — — 15 Naugard 445 ® Antioxidant0.5 0.5 0.5 Irgacure ® 1800 Photoinitiator 1 1 1 Physical PropertiesHardness, Shore A (pts) 69 68 65 Surface Exposed to Radiation Hardness,Shore A (pts) 61 59 55 Surface Away from Source Compression Set (%) 2530 90 22 hours @ 150° C., 25% deflection

Example 5 and Comparative Example A

Three curable compositions of the present invention, Samples 5A, 5B, and5C, were prepared by mixing on a rubber mill of a copolymer of ethyleneand methyl acrylate (ethylene content 34 wt. %, Mooney viscosity ML1+4(100° C.) of 8) and the components shown in Table V. Uncured slabs of 6mm thickness were shaped by molding in a mold coated with Teflon®fluoropolymer resin. The resultant polymers were exposed for 2 minutesto UV radiation from a medium pressure mercury lamp, which emittedradiation of wavelength approximately 250-400 nm at a power of 80 W/cm.The distance of the samples from the lamp during the curing process was10 cm. Shore A hardness of the surface of the 6 mm slabs exposed to thelamp and the surface facing away from the lamp were determined. Inaddition, compression set of the cured compositions was determinedaccording to ISO 815 on specimens died out of the 6 mm slabs. Tensilestrength, modulus, and elongation at break were determined according toISO 37 T2 on 2 mm specimens. Results are shown in Table V. For purposesof comparison, a composition was prepared which contained a peroxidecure system. This composition was also prepared in the same manner asSamples 5A-5C. The components of the composition, labeled Sample A, areshown in Table V. Sample A was press cured at 180° C. for 4 minutes andphysical properties of the cured composition were determined in the samemanner as those of Samples 5A-5C. Compression molding of the controlsample resulted in formation of blisters in the specimen and thephysical properties of the sample were therefore difficult to determine.

TABLE V Sample Composition¹ 5A 5B 5C A Polymer 88 92.5 95 100Trimethylolpropane triacrylate 10 7.5 5 — Irgacure ® 1800 Photoinitiator0.75 0.75 0.75 — N,N′-m-Phenylenedimaleimide — — — 2 Peroxide² — — — 5Naugard ® 445 Antioxidant 0.5 0.5 0.5 0.5 Physical Properties Time ofExposure to UV Light 2 2 2 — (Minutes) Press Cure @ 160° C. (Minutes) —— — 30 Hardness, Shore A (pts) 59 50 42 30 Surface Exposed to RadiationHardness, Shore A (pts) 56 42 38 — Surface Away From Source T_(B) (MPa)³4.7 3.8 2.7 1.1 M₁₀₀ (MPa)⁴ 2.2 1.2 0.6 0.5 M₂₀₀ (MPa)⁵ 4.1 2.6 0.9 0.8E_(B) (%)⁶ 250 317 450 250 Compression Set (%) 25 33 38 85 168 hours,150° C., 25% deflection ¹In parts by weight.²Bis(t-butylperoxy)diisopropylbenzene (40% on inert support). ³TensileStrength at Break ⁴Modulus at 100% elongation ⁵Modulus at 200%elongation ⁶Elongation at break

Example 6

A curable elastomeric composition of the invention, Sample 6, wasprepared by mixing on a rubber mill 88 parts of a copolymer of ethyleneand methyl acrylate (ethylene content 34 wt. %, Mooney viscosity ML1+4(100° C.) of 8), 12 parts trimethylolpropane triacrylate, 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)-diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 6 mm thickness and 2 mm thickness were shaped bymolding in a mold coated with Teflon® fluoropolymer resin. Samples ofboth the 2 mm thick slabs and the 6 mm thick slabs were exposed for 240seconds to UV radiation from a medium pressure mercury lamp, whichemitted radiation of wavelength approximately 300-400 nm at 80 watts/cm.The distance of the samples from the lamp during the curing process was10 cm. The cured samples exhibited the hardness and compression setproperties shown in Table VI. Test specimens of the cured compositionwere died out of the 6 mm slabs and used for compression set testing.Samples for tensile, modulus, and elongation testing were died out ofthe 2 mm slabs. Physical properties are shown in Table VI.

TABLE VI Composition (phr) Sample 6 Polymer 88 Naugard ® 445 Antioxidant0.5 Trimethylolpropane triacrylate 12 Irgacure ® 1800 photoinitiator0.75 Hardness, Shore A (6 mm thick specimens) Surface Exposed toRadiation (pts) 63 Surface Away from Source (pts) 56 Compression Set (%)25% deflection After 170 hours in air at 150° C. 24 After 500 hours inair at 150° C. 35 After 1000 hours in air at 150° C. 48 After 170 hoursin engine oil at 150° C. 11 After 500 hours in engine oil at 150° C. 24After 1000 hours in engine oil at 150° C. 45 Physical Properties (2 mmthick specimens, room temperature) T_(B) (MPa) 7.9 M₁₀₀ (MPa) 4.0 E_(B)(%) 366 Hardness, Shore A (pts) 60 Physical Properties (2 mm thickspecimens, aged at 150° C. for 1000 hours in air) T_(B) (MPa) 7.2 M₁₀₀(MPa) 4.3 E_(B) (%) 337 Hardness, Shore A (pts) 63 Physical Properties(2 mm thick specimens, aged at 150° C. for 1000 hours in engine oil¹⁾T_(B), (MPa) 7.3 M₁₀₀ (MPa) 4.9 E_(B) (%) 196 Hardness, Shore A (pts) 57¹⁾Shell Helix Plus ® 10W/40 Oil

Example 7

A curable elastomeric composition of the invention, Sample 7, wasprepared by mixing on a rubber mill 88 parts of a copolymer of ethyleneand methyl acrylate (ethylene content 34 wt. %, Mooney viscosity ML1+4(100° C.) of 8), 12 parts trimethylolpropane triacrylate, 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)-diphenylamine, available from Uniroyal,Inc.). The composition was introduced to a 20 liter steel drum melter.The piston, which was maintained at a temperature of 140° C., heated andsoftened the composition while delivering it, at a pressure of 3.5 bars,to a gear pump which continuously fed a stream to a volumetricapplication gun mounted on an industrial robot. The composition wasapplied during a period of less than 15 seconds to the groove of athermoplastic automobile engine cover. The groove had a total length ofapproximately 1.2 m. The cover was conveyed under a medium pressuremercury lamp having wavelength approximately 250-400 nm and a powerrating of 100 W/cm. The lamp was approximately 15 cm from the surface ofthe curable composition. Exposure was for approximately 40 seconds. Thecomposition was sufficiently cured to exhibit a Shore A hardness of55-60.

Example 8

A curable elastomeric composition of the invention was prepared bymixing on a rubber mill 92.5 parts of a copolymer of butadiene andacrylonitrile (acrylonitrile content 41 wt. %; Mooney viscosity ML 1+4(100° C.) of 80), 7.5 parts trimethylolpropane triacrylate, 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 2 mm and 6 mm thickness were shaped by moldingin a mold coated with Teflon® fluoropolymer resin. The resultant 2 mmand 6 mm slabs were exposed for two minutes to UV radiation from amedium pressure mercury lamp (80 W/cm) that emitted radiation ofwavelength approximately 250-400 nm at a distance of 10 cm from thelamp. Shore A hardness of the surface exposed to the lamp and thesurface facing away from the lamp of the 6 mm slabs were determined.Tensile strength, modulus, and elongation at break of the curedcompositions died from the 2 mm slab were determined according to ISO 37T2. Results are shown in Table VII.

TABLE VII Composition (phr) Sample 8 Polymer 92.5 Naugard ® 445Antioxidant 0.5 Trimethylolpropane triacrylate 7.5 Irgacure ® 1800photoinitiator 0.75 Hardness, Shore A (6 mm thick specimens) SurfaceExposed to Radiation 49 Surface Away from Source (pts) 39 PhysicalProperties (2 mm thick specimens) T_(B) (MPa) 1.7 M₁₀₀ (MPa) 1.1 E_(B)(%) 174

Example 9

A curable elastomeric composition of the invention was prepared bymixing on a rubber mill 92.5 parts of a hydrogenated copolymer ofbutadiene and acrylonitrile (acrylonitrile content 33.5 wt. %; Mooneyviscosity ML 1+4 (100° C.) of 70; double bond content less than 1%), 7.5parts trimethylolpropane triacrylate, 0.75 parts Irgacure® 1800photoinitiator (a mixture of 75 wt. % 1-hydroxy-cyclohexyl phenyl ketoneand 25 wt. % bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphineoxide, available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445antioxidant (4,4′-di(α, α-dimethylbenzyl)diphenylamine, available fromUniroyal, Inc.). Uncured slabs of 2 mm and 6 mm thickness were shaped bymolding in a mold coated with Teflon® fluoropolymer resin. The resultant2 mm and 6 mm slabs were exposed for two minutes to UV radiation from amedium pressure mercury lamp which emitted radiation of wavelengthapproximately 250-400 nm at a distance of 10 cm from the lamp. Shore Ahardness of the surface exposed to the lamp and the surface facing awayfrom the lamp of the 6 mm slabs were determined. Tensile strength,modulus, and elongation at break of the cured compositions died from the2 mm slab were determined according to ISO 37 T2. Results are shown inTable VIII.

TABLE VIII Composition (phr) Sample 9 Polymer 92.5 Naugard ® 445Antioxidant 0.5 Trimethylolpropane triacrylate 7.5 Irgacure ® 1800photoinitiator 0.75 Hardness, Shore A (6 mm thick specimens) SurfaceExposed to Radiation 53 Surface Away from Source (pts) 39 PhysicalProperties (2 mm thick specimens) T_(B) (MPa) 5.8 M₁₀₀ (MPa) 1.2 E_(B)(%) 516

Example 10

A curable elastomeric composition of the invention was prepared bymixing on a rubber mill 92.5 parts of Therban® XN 535C (a hydrogenatedterpolymer of butadiene, acrylonitrile, and a termonomer, available fromBayer AG), 7.5 parts trimethylolpropane triacrylate, 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 2 mm and 6 mm thickness were shaped by moldingin a mold coated with Teflon® fluoropolymer resin. The resultant 2 mmand 6 mm slabs were exposed for two minutes to UV radiation from amedium pressure mercury lamp (80 W/cm) that emitted radiation ofwavelength approximately 250-400 nm at a distance of 10 cm from thelamp. Shore A hardness of the surface exposed to the lamp and thesurface facing away from the lamp of the 6 mm slabs were determined.Tensile strength, modulus, and elongation at break of the curedcompositions died from the 2 mm slab were determined according to ISO 37T2. Results are shown in Table IX.

TABLE IX Composition (phr) Sample 10 Polymer 92.5 Naugard ® 445Antioxidant 0.5 Trimethylolpropane triacrylate 7.5 Irgacure ® 1800photoinitiator 0.75 Hardness, Shore A (6 mm thick specimens) SurfaceExposed to Radiation 42 Surface Away from Source (pts) 36 PhysicalProperties (2 mm thick specimens) T_(B) (MPa) 4.6 M₁₀₀ (MPa) 1.1 E_(B)(%) 351

Example 11

A curable elastomeric composition of the invention, Sample 11 A, wasprepared by mixing on a rubber mill 92.5 parts of a copolymer ofethylene and methyl acrylate (ethylene content 34 wt. %, Mooneyviscosity ML(1+4 @ 100° C. of 8), 7.5 parts pentaerythritoltetraacrylate (Sartomer 295, available from Sartomer, Inc.), 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. %1-hydroxy-cyclohexyl phenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 6 mm thickness and 2 mm thickness were shaped bymolding in a mold coated with Teflon® fluoropolymer resin. Samples ofthe 2 mm thick slabs thick slabs were exposed for 120 seconds to UVradiation from a medium pressure mercury lamp (80 W/cm), which emittedradiation of wavelength greater than 250 nm. Samples of the 6 mm thickslabs thick slabs were similarly exposed for 240 seconds. The distanceof the samples from the lamp during the curing process was 10 cm. Thecured samples exhibited the hardness and compression set propertiesshown in Table X. Test specimens of the cured composition were died outof the 6 mm slabs and used for compression set testing. Samples fortensile, modulus, and elongation testing were died out of the 2 mmslabs. Physical properties are shown in Table X. Samples 11B, C, and Dwere similarly prepared using the ingredients shown in Table X. Testresults for Samples are 11B-D are also shown in Table X.

TABLE X Composition (phr) 11A 11B 11C 11D Polymer 92.5 92.5 92.5 92.5Pentaerythritol Tetraacrylate¹ 7.5 5 0 0 Pentaerythritol Pentaacrylate²0 0 7.5 5 Naugard ® 445 Antioxidant 0.5 0.5 0.5 0.5 Irgacure ® 1800Photoinitiator 0.75 0.75 0.75 0.75 Hardness, Shore A (6 mm thickspecimens) Surface exposed to radiation (pts) 52 39 52 44 Surface awayfrom source (pts) 45 37 46 39 Compression Set (%) 30 39 32 39 168 hours@ 150° C. in air Physical Properties (2 mm thick specimens)³ M₁₀₀ (MPa)1.6 0.6 1.7 0.8 T_(B) (MPa) 4.3 2.7 3.9 3.3 E_(B) (%) 236 383 200 332Hardness, Shore A Surface 50 40 50 43 exposed to radiation (pts)¹Sartomer 295 (pentaerythritol tetraacrylate, available from Sartomer,Inc. ²Sartomer 399 (dipentaerythritol pentaacrylate, available fromSartomer, Inc. ³Stress/strain properties measured according to ISO 37-T2@ room temperature

Example 12

A curable elastomeric composition of the invention, Sample 12A, wasprepared by mixing on a rubber mill 92.5 parts of Therban® A 4307 Rubber(a hydrogenated copolymer of butadiene and acrylonitrile, available fromBayer AG), 7.5 parts trimethylolpropane triacrylate, 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)-diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 2 mm thickness were shaped by molding in a moldcoated with Teflon® fluoropolymer resin. The resultant 2 mm slabs wereexposed for four minutes to UV radiation from a medium pressure mercurylamp (80 W/cm) which emitted radiation of wavelength greater than 250 nmat a distance of 10 cm from the lamp. Shore A hardness, tensilestrength, modulus, and elongation at break of the cured compositionsdied from the 2 mm slab were determined according to ISO 37 T2 at roomtemperature. Results are shown in Table XI. Two further compositions ofthe invention, Samples 12B and 12C, were prepared in a similar fashionusing the proportion of components shown in Table XI. Test specimenswere prepared as described for Sample 12 A and results are shown inTable XI.

TABLE XI Sample Sample Sample Composition (phr) 12A 12B 12C Polymer 92.592.5 92.5 Naugard ® 445 Antioxidant 0.5 0.5 0.5 Trimethylolpropanetriacrylate 7.5 7.5 7.5 Irgacure ® 1800 photoinitiator 0.75 1.2 2Physical Properties (2 mm thick specimens) T_(B) (MPa) 8.5 6.5 7 M₁₀₀(MPa) 1.5 1.2 1.3 E_(B) (%) 490 420 420 Hardness Shore A 58 58 58Surface exposed to radiation (pts) Compression Set (%) 168 hours @ 75 6258 150° C. in air

Example 13

A curable elastomeric composition of the invention, Sample 13, wasprepared substantially in the same manner and using the same componentsas Sample 12B except that 92.5 parts of Therban® Rubber A 4367 (ahydrogenated copolymer of butadiene and acrylonitrile, available fromBayer AG; acrylonitrile content 43 wt. %; Mooney viscosity ML 1+4 (100°C.) of 70; double bond content 5.5%), was used in place of Therban® A4307 as the polymer component. Uncured slabs of 2 mm thickness wereshaped by molding in a mold coated with Teflon® fluoropolymer resin. Theresultant 2 mm slabs were exposed for four minutes to UV radiation froma medium pressure mercury lamp (80 W/cm) that emitted radiation ofwavelength greater than 250 nm at a distance of 10 cm from the lamp.Tensile strength, modulus, and elongation at break of the curedcompositions died from the 2 mm slab were determined according to ISO 37T2 at room temperature. Results are shown in Table XII. Test specimenswere prepared as described for Sample 12 A and results are shown inTable XII.

TABLE XII Composition (phr) Sample 12B Sample 13 Therban ® A 4307 Rubber92.5 0 Therban ® A 4367 Rubber 0 92.5 Naugard ® 445 Antioxidant 0.5 0.5Trimethylolpropane triacrylate 7.5 7.5 Irgacure ® 1800 photoinitiator1.2 1.2 Physical Properties (2 mm thick specimens) T_(B) (MPa) 6.5 5.7M₁₀₀ (MPa) 1.2 1.6 E_(B) (%) 420 320 Hardness Shore A 58 59 Surfaceexposed to radiation (pts) Compression Set (%) 168 hours @ 62 53 150° C.in air

Example 14

A curable elastomeric composition of the invention, Sample 14A, wasprepared by mixing on a rubber mill 92.5 parts of Elvaloy® 742 resinmodifier (a copolymer of ethylene, vinyl acetate and carbon monoxidecontaining 28.5 wt. % vinyl acetate units, and 9 wt. % carbon monoxideunits, having a melt index of 35 g/10 minutes, available from E. I. duPont de Nemours and Co.), 7.5 parts trimethylolpropane triacrylate, and0.75 parts Irgacure® 1800 photoinitiator (a mixture of 75 wt. %1-hydroxycyclohexyl phenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.) Uncured slabs of 2 mm thickness wereshaped by molding in a mold coated with Teflon® fluoropolymer resin. Theresultant 2 mm slabs were exposed for two minutes to UV radiation from amercury lamp (80 W/cm) that emitted radiation of wavelength greater than250 nm at a distance of 10 cm from the lamp. Shore A hardness of thesurface exposed to the lamp and the surface facing away from the lampwere determined. Tensile strength, modulus, and elongation at break ofthe cured compositions died from the 2 mm slab were determined accordingto ISO 37 T2. Results are shown in Table XIII. In addition, Samples 14Band 14C were prepared and tested in a similar manner. Sample 14Bcontained Elvaloy® HP 661 resin modifier (a copolymer of ethylene, butylacrylate and carbon monoxide containing 29 wt. % butyl acrylate units,and 10 wt. % carbon monoxide units, having a melt index of 12 g/10minutes, available from E. I. du Pont de Nemours and Co.) as thepolymeric component. Sample 14C contained Elvaloy® AS resin modifier (acopolymer of ethylene, n-butyl acrylate and glycidyl methacrylatecontaining 28 wt. % n-butyl acrylate units, and 5.25 wt. % glycidylmethacrylate units, having a melt index of 12 g/10 minutes, availablefrom E. I. du Pont de Nemours and Co.) as the polymeric component.Physical test results are shown in Table XIII.

TABLE XIII Composition 14A 14B 14C Elvaloy ® 742 resin modifier 92.5 0 0Elvaloy ® HP 661 resin modifier 0 92.5 0 Elvaloy ® AS resin modifier 0 092.5 Trimethylolpropane triacrylate 7.5 7.5 7.5 Irgacure ® 1800photoinitiator 0.75 0.75 0.75 Hardness, Shore A (2 mm thick specimens)Uncured Hardness (points) 58 64 65 Surface Exposed to Radiation (points)68 68 72 Surface Away from Source (points) 66 67 71 Physical Properties(2 mm thick specimens) T_(B) (MPa) 9.6 7.8 9.9 M₁₀₀ (MPa) 3.9 3.1 3.1E_(B) (%) 350 420 600 Compression Set, (%), 70 hours @ 42 28 32 125° C.

Example 15

A curable elastomeric composition of the invention was prepared bymixing on a rubber mill 90.3 parts of a copolymer of ethylene and methylacrylate (ethylene content 34 wt. %, Mooney viscosity ML 1+4 (100° C.)of 8), 8.46 parts trimethylolpropane triacrylate, 0.75 parts Irgacure®1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexyl phenylketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), 0.49 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethyl-benzyl)-diphenylamine, available from Uniroyal,Inc.), and 5 parts of Celogen® OT blowing agent[p,p′-oxybis(benzenesulfonyl hydrazide), available from Uniroyal, Inc.].Uncured slabs of 2 mm thickness were shaped by molding in a mold coatedwith Teflon® fluoropolymer resin. The slabs were exposed for 4 minutesto UV radiation from a medium pressure mercury lamp (80 W/cm) thatemitted radiation of wavelength greater than 250 nm. The distance of thesamples from the lamp was 10-15 cm. The temperature of the cured samplesat the conclusion of UV exposure was 140°-150° C. A foam having a closedcell structure with integral skin was formed having specific gravitydown to 0.3 g/cm.

Example 16

A curable elastomeric composition of the invention, Sample 16A, wasprepared by mixing the following components on a rubber mill: 94 partsof a copolymer of vinylidene fluoride (VF₂), perfluoromethylperfluorovinyl ether (PMVE), tetrafluoroethylene (TFE), and4-bromo-3,3,4,4-tetrafluorobutene-1 (BTFB) (weight ratioVF₂:TFE:PMVE:BTFB 54:10:35:1.2), 6.0 parts trimethylolpropanetriacrylate, and 0.5 parts Irgacure 1800® photoinitiator. The milledcomposition was shaped into uncured slabs of 2 mm thickness were shapedby molding in a mold coated with Teflon® fluoropolymer resin. An uncuredslab was exposed for one minute to UV radiation from a medium pressuremercury lamp that emitted radiation of wavelength approximately 250-400nm at 80 watts/cm. The distance of the samples from the lamp was 10 cm.The cured samples exhibited the properties shown in Table XIV. Twoadditional samples, 16B and 16C, were prepared in substantially the samemanner except that Sample 16B contained 8 parts of trimethylolpropanetriacrylate and Sample 16C contained 0.5 parts tri-n-butyltin hydride inaddition to the 6 parts of trimethylolpropane triacrylate. Samples 16Band 16C were cured substantially in the same manner as Sample 16A.Physical properties of the cured slabs are shown in Table XIV.

TABLE XIV Sample Composition 16A 16B 16C Polymer 94 92 94Trimethylolpropane triacrylate 6 8 6 Irgacure ® 1800 Photoinitiator 0.50.5 0.5 Tri-n-butyltin hydride — — 0.5 Physical Properties Hardness,Shore A (pts) 59 70 — Surface Exposed to Radiation Hardness, Shore A(pts) Surface Away From Source T_(B) (MPa) 9.1 10.9 13.8 M₁₀₀ (MPa) 3.15.4 7 E_(B) (%) 450 339 273 Compression Set (%) 69 — 36 22 hours, 150°C., 25% deflection, 2 minute UV exposure

Example 17

A curable elastomeric composition of the invention, Sample 17A, wasprepared by mixing the following components on a rubber mill: 94 partsof an iodinated copolymer VF₂, PMVE, TFE, and BTFB (weight ratioVF₂:TFE:PMVE:BTFB 54:10:35:0.6; prepared in the presence of an iodinatedchain transfer agent and having an iodine content of 0.18), 6.0 partstrimethylolpropane triacrylate, and 1 part Irgacure 1800®photoinitiator. The milled composition was shaped into uncured slabs of2 mm thickness were shaped by molding in a mold coated with Teflon®fluoropolymer resin. An uncured slab was exposed for one minute to UVradiation from a medium pressure mercury lamp which emitted radiation ofwavelength approximately 250-400 nm at 80 watts/cm. The distance of thesamples from the lamp was 10 cm. The cured samples exhibited theproperties shown in Table XV. Three additional samples, 17B, 17C, and17D, were prepared in substantially the same manner except that eachcontained 0.5 parts of Irgacure 1800, Sample 17B contained 94 parts ofan iodine-free copolymer of VF₂, PMVE, TFE, and BTFB having a monomerratio of 54:10:35:1.2; Sample 17C contained 94 parts of an iodine-freecopolymer of VF₂, PMVE, TFE, and BTFB having a monomer ratio of52.9:10.2:34.9:2.2; and Sample 17D contained 94 parts of an iodine-freecopolymer of VF₂, PMVE, TFE, and BTFB having a monomer ratio of53.5:10:34.4:2.2. Samples 17B-17D were cured substantially in the samemanner as Sample 3A. Physical properties of the cured slabs are shown inTable XV.

TABLE XV Sample Composition 17A 17B 17C 17D Polymer 94 94 94 94Trimethylolpropane triacrylate 6 6 6 6 Irgacure ® 1800 Photoinitiator 10.5 0.5 0.5 Physical Properties Hardness, Shore A (pts) 49 59 60 —Surface Exposed to Radiation T_(B) (MPa) 2 9.1 7.5 9.9 M₁₀₀ (MPa) 1.43.1 3.3 3.8 E_(B) (%) 537 450 346 431 Compression Set (%) — 69 75.3 76.222 hours, 150° C., 25% deflection, 2 minute UV exposure

Example 18

A curable elastomeric composition of the invention, Sample 18A, wasprepared by mixing the following components on a rubber mill: 92 partsof a copolymer VF₂, PMVE, TFE, and BTFB (weight ratio VF₂:TFE:PMVE:BTFB52.9:10.2:34.9:2.0), 8.0 parts trimethylolpropane triacrylate, and 0.5parts Irgacure 1800® photoinitiator. The milled composition was shapedinto uncured slabs of mm thickness were shaped by molding in a moldcoated with Teflon® fluoropolymer resin. An uncured slab was exposed forone minute to UV radiation from a medium pressure mercury lamp whichemitted radiation of wavelength approximately 250-400 nm at 80 watts/cm.The distance of the samples from the lamp was 10 cm. The cured samplesexhibited the properties shown in Table XVI. An additional sample, 18B,was prepared in substantially the same manner. However, Sample 18Bcontained 100 parts polymer and additionally contained 0.5 partstri-n-butyltin hydride. Sample 18B was cured substantially in the samemanner as Sample 18A. Physical properties of the cured slabs are shownin Table XVI.

TABLE XVI Sample Composition 18A 18B Polymer 92 100 Trimethylolpropanetriacrylate 8 8 Irgacure ® 1800 Photoinitiator 0.5 0.5 Tri-n-butyltinHydride — 0.5 Physical Properties Hardness, Shore A (pts) — 68 SurfaceExposed to Radiation T_(B) (MPa) 10 11.8 M₁₀₀ (MPa) 6 6.3 E_(B) (%) 284239 Compression Set (%) 74.4 35.4 22 hours, 120 C., 25% deflection, 2minute UV exposure

Example 19

A curable elastomeric composition of the invention, Sample 19A, wasprepared by mixing the following components on a rubber mill: 92 partsof a copolymer VF₂, PMVE, TFE, and BTFB (weight ratio VF₂:TFE:PMVE:BTFB53.5:10:34.4:2.2), 8.0 parts trimethylolpropane triacrylate, and 0.5parts Irgacure 1800® photoinitiator. The milled composition was shapedinto uncured slabs of 2 mm thickness were shaped by molding in a moldcoated with Teflon® fluoropolymer resin. An uncured slab was exposed forone minute to UV radiation from a medium pressure mercury lamp whichemitted radiation of wavelength approximately 250-400 nm at 80 watts/cm.The distance of the samples from the lamp was 10 cm. The cured samplesexhibited the properties shown in Table XVII. An additional sample, 19B,was prepared in substantially the same manner. However, Sample 19Bcontained 100 parts polymer, 1 part Irgacure 1800® photoinitiator andadditionally contained 1 part tri-n-butyltin hydride. Sample 19B wascured substantially in the same manner as Sample 19A. Physicalproperties of the cured slabs are shown in Table XVII.

TABLE XVII Sample Composition 19A 19B Polymer 92 100 Trimethylolpropanetriacrylate 8 8 Irgacure ® 1800 Photoinitiator 0.5 1.0 Tri-n-butyltinHydride — 0.5 Physical Properties Hardness, Shore A (pts) 61 71 SurfaceExposed to Radiation T_(B) (MPa) 9.9 11.8 M₁₀₀ (MPa) 5.7 7.3 E_(B) (%)356 215 Compression Set (%) 71.5 43.3 22 hours, 150° C., 25% deflection,2 minute UV exposure

Example 20

A curable elastomeric composition of the invention, Sample 20, wasprepared by mixing the following components on a rubber mill: 90 partsof a chlorosulfonated polyethylene elastomer [chlorine content 29 wt. %,sulfur content of 1.4 wt. % and a Mooney viscosity, ML 1+4 (100° C.) of22], 10.0 parts trimethylolpropane triacrylate, and 0.5 parts Irgacure®184 photoinitiator (1-hydroxycyclohexyl phenyl ketone, available fromCiba Geigy, Inc.). The milled composition was shaped into uncured slabsof 2 mm thickness for tensile testing specimens and 6 mm thickness forcutting compression set disks. The slabs were shaped by molding in amold coated with Teflon® fluoropolymer resin. The uncured slabs wereexposed to UV radiation from a medium pressure mercury lamp whichemitted radiation of wavelength approximately 250-400 nm at 80 watts/cm.The 2 mm slabs were exposed for 4 minutes and the 6 mm slabs wereexposed for 6 minutes. Exposure was effected under water to limit theheat build-up in the elastomeric composition which could cause excessivedehydrochlorination and polymer degradation. The distance of the samplesfrom the lamp was 10 cm. The cured samples exhibited the propertiesshown in Table XVIII.

TABLE XVIII Sample Composition 20 Polymer 90 Trimethylolpropanetriacrylate 10 Irgacure ® 184 Photoinitiator 0.5 Physical PropertiesHardness,¹ Shore A (pts) 63 Surface Exposed to Radiation Hardness,¹Shore A (pts) 61 Surface Away From Source T_(B) (MPa) 4.7 M₁₀₀ (MPa) 3.6E_(B) (%) 128 Compression Set (%) 57 70 hours, 125° C., 25% deflection,4 minute UV exposure ¹6 mm slabs in water

Example 21

A curable elastomeric composition of the invention, Sample 21, wasprepared by mixing the following components on a rubber mill: 85 partsof a chlorinated polyethylene elastomer [chlorine content 36 wt. % and aMooney viscosity, ML 1+4 (121° C.) of 36], 15 parts trimethylolpropanetriacrylate, 1 part Irgacure 1800® photoinitiator and 0.5 parts Naugard®445 antioxidant (4,4′-bis-(α, α-dimethylbenzyl)diphenylamine). Themilled composition was shaped into uncured slabs of 2 mm thickness forpreparation of tensile specimens and 6 mm thickness for cuttingcompression set disks. The slabs were shaped by molding in a mold coatedwith Teflon® fluoropolymer resin. An uncured slab was exposed for 4minutes, under water, to limit the heat build-up in the elastomericcompositions, to UV radiation from a medium pressure mercury lamp whichemitted radiation of wavelength approximately 250-400 nm at 80 watts/cm.The distance of the samples from the lamp was 10 cm. The cured samplesexhibited the properties shown in Table XIX.

TABLE XIX Sample Composition 21 Polymer 85 Trimethylolpropanetriacrylate 15 Irgacure ® 1800 Photoinitiator 1.0 Naugard ® 445Antioxidant 0.5 Physical Properties Hardness,¹ Shore A (pts) 94 SurfaceExposed to Radiation Hardness,¹ Shore A (pts) 91 Surface Away FromSource T_(B) (MPa) 10.9 E_(B) (%) 93 Compression Set (%) 58 70 hours,125° C., 25% deflection, 4 minute UV exposure, 6 mm slab ¹6 mm slabs inwater

Example 22

A curable elastomeric composition of the invention, Sample 22, wasprepared by mixing the following components on a rubber mill: 90 partsof Hydrin® C 2000L epichlorohydrin elastomer (anepichlorohydrin/ethylene oxide copolymer, chlorine content 26 wt. %,Mooney viscosity 65, available from Nippon Zeon, Inc.], 10.0 partstrimethylolpropane triacrylate, and 0.75 parts Irgacure 184®photoinitiator (1-hydroxycyclohexyl phenyl ketone, available from CibaGeigy, Inc.). The milled composition was shaped into uncured slabs of 2mm thickness for preparation of tensile specimens and 6 mm thickness forcutting compression set disks. The slabs were shaped by molding in amold coated with Teflon® fluoropolymer resin. An uncured slab wasexposed for 4 minutes in water to UV radiation from a medium pressuremercury lamp which emitted radiation of wavelength approximately 250-400nm at 80 watts/cm. The distance of the samples from the lamp was 10 cm.The cured samples exhibited the properties shown in Table XX.

TABLE XX Sample Composition 22 Polymer 90 Trimethylolpropane triacrylate10 Irgacure ® 184 Photoinitiator 0.75 Physical Properties Hardness,¹Shore A (pts) 54 Surface Exposed to Radiation Hardness,¹ Shore A (pts)50 Surface Away From Source T_(B) (MPa) 4.6 M₁₀₀ (MPa) 3.3 E_(B) (%) 187Compression Set (%) 24 70 hours, 120° C., 25% deflection, 4 minute UVexposure ¹6 mm slabs in water

We claim:
 1. A thermally stable, UV curable elastomer compositioncomprising A) 70 to 99 weight percent of a fluoroelastomer having atleast one cure site selected from the group consisting of 1)copolymerized brominated olefins, chlorinated olefins and iodinatedolefins; 2) copolymerized brominated unsaturated ethers, chlorinatedunsaturated ethers, and iodinated unsaturated ethers; 3) copolymerizednon-conjugated dienes and trienes and 4) iodine atoms and bromine atomsand mixtures thereof that are present at terminal positions of thefluoroelastomer chain; B) 0.5 to 20 weight percent of a multifunctionalcrosslinking agent selected from the group consisting of multifunctionalacrylic crosslinking agents, multifunctional methacrylic crosslinkingagents, multifunctional cyanurate crosslinking agents, andmultifunctional isocyanurate crosslinking agents; and C) 0.1 to 10weight percent of a UV initiator wherein the weight percentages of eachof components A), B), and C) are based on the combined weight ofcomponents A), B), and C).
 2. The composition of claim 1 wherein thefluoroelastomer is a copolymer comprising copolymerized units ofvinylidene fluoride.
 3. The composition of claim 1 wherein thefluoroelastomer is a copolymer comprising copolymerized units oftetrafluoroethylene.
 4. The composition of claim 1 wherein the cure siteis selected from the group consisting of copolymerized brominatedolefins, chlorinated olefins and iodinated olefins.
 5. The compositionof claim 1 wherein at least one cure site is selected from the groupconsisting of copolymerized brominated unsaturated ethers, chlorinatedunsaturated ethers, and iodinated unsaturated ethers.
 6. The compositionof claim 1 wherein at least one cure site is selected from the groupconsisting of copolymerized non-conjugated dienes.
 7. The composition ofclaim 1 wherein at least one cure site is selected from the groupconsisting of iodine atoms and bromine atoms and mixtures thereof thatare present at terminal positions of the fluoroelastomer chain.
 8. Thecomposition of claim 1 having a cure site that is a brominated olefin.9. The composition of claim 8 wherein the cure site is4-bromo-3,3,4,4-tetrafluoro-1-butene.
 10. The composition of claim 1wherein the multifunctional crosslinking agent is a multifunctionalacrylic crosslinking agent.
 11. The composition of claim 1 wherein themultifunctional crosslinking agent is a multifunctional methacryliccrosslinking agent.
 12. The composition of claim 1 wherein the UVinitiator is a ketone.
 13. The composition of claim 1 wherein themultifunctional crosslinking agent is a multifunctional cyanuratecrosslinking agent.
 14. The composition of claim 1 wherein themultifunctional crosslinking agent is a multifunctional isocyanuratecrosslinking agent.